(CNN) -- Accused by the top U.S. diplomat of "propping up the regime" of Syria's embattled president, Russian officials struck back Friday by denying arms sales to Damascus and claiming international efforts may have fostered instability and violence.
A day after making those accusatory remarks, U.S. Secretary of State Hillary Clinton on Friday hammered home her claim that Moscow is helping its longtime ally in Damascus through a "very consistent arms trade" that "has strengthened (President Bashar al-Assad's) regime."
"The fact that Russia has continued to sustain this trade in the face of efforts by the international community to impose sanctions and to prevent further arms flowing to the Assad regime, and in particular the Syrian military, has raised serious concerns on our part," Clinton said from Oslo, Norway.
Russian President Vladimir Putin responded hours later by flatly denying "any trading connections (or) military" with its longtime ally Syria.
"The only thing that concerns us in (Syria) is the possibility of radicalization of the situation, the situation getting out of control and the deaths of civilians," Putin said from France, after meeting new French President Francois Hollande.
"Our aim is to bring the conflict to peace. We are not dividing them into ours and not ours."
Russian Foreign Ministry spokesman A.K. Lukashevich earlier Friday spoke even more forcefully, asserting that some international efforts -- including threats of military intervention -- have exacerbated the crisis, pushing Syria closer to civil war and making it easier for "strong religious elements (to) come to the forefront."
"They still give preference to their own agenda, where the change of the ruling regime in Damascus remains the main point," the spokesman said of unnamed "international and regional players" calling for al-Assad's ouster.
They include Hollande who, standing next to Putin, on Friday accused the Syrian president of acting "in an unacceptable and intolerable way" and said he must go.
"There will only be an exit possible with the departure of Bashar al-Assad," he said.
Speaking earlier Friday in Berlin after meeting Chancellor Angela Merkel, Putin said that Russia "will maintain contact with President Assad and the leadership of Syria and with regional countries, Arab countries ... in order to find a political solution."
He later warned against the international community acting rashly, especially militarily.
"What happened in Libya and Iraq? ... Have they become safer and better? Where are they moving? Is there an answer? Nobody has it as of yet," Putin said from France. "That's why we're proposing, at least in Syria, to act carefully."
Russia's foreign ministry spokesman also weighed in on last week's massacre in the Syrian city of Houla.
Calling it "a barbaric crime (that deserves) an extremely severe punishment," he said the identity of the perpetrators hasn't been determined yet -- though the U.N. Human Rights Council has noted preliminary reports of government involvement.
Lukashevich alluded to Moscow's concerns that outside forces may be behind such attacks and pointed to the Syrian government's investigation that found "this crime was a well-planned act on behalf of militants with the aim of torpedoing efforts to achieve a political settlement."
"The tragedy in Houla has shown what may result from financial aid to militants, smuggling in modern armament systems for them, recruiting foreign mercenaries and flirting with extremists of all kinds," the Russian spokesman said.
Meanwhile, the Human Rights Council on Friday authorized the U.N.'s Independent International Commission of Inquiry on Syria -- which has issued ongoing reports about violence in the country -- to conduct a robust probe into the Houla killings, said council spokesman Rupert Colville.
Meeting in Geneva, Switzerland, 41 countries voted for the resolution while Russia, China and Cuba voted against it. Russia and China have blocked tough U.N. Security Council targeting al-Assad's government.
Before the vote, U.N. Human Rights commissioner Navi Pillay called for unimpeded access for an investigation into the massacre, which left 108 people, including 49 children, dead.
Syria told Pillay's office that "terrorist armed groups" were responsible for Houla. It said the military "was acting only in self-defense, and that it sought to protect the civilian population."
She said the massacre "may amount to crimes against humanity and other international crimes, and may be indicative of a pattern of widespread or systematic attacks against civilian populations that have been perpetrated with impunity."
"Once again, I urge the Security Council to consider referring the case of Syria to the International Criminal Court," Pillay said.
Reports of more carnage filtered out of Syria on Friday, with at least 37 people slain across the country, the opposition Local Coordination Committees of Syria said.
The crisis in Syria began nearly 15 months ago when a tough government crackdown launched against protesters last year spiraled out of control and spawned a national anti-government uprising. It is estimated that between 9,000 and more than 14,000 Syrians have died since then.
Fresh reports of terror have emerged this week. In the Homs province village of Bouyda, 12 factory workers were killed Thursday by pro-government gangs known as Shabiha, the opposition Syrian Observatory for Human Rights said. They were lined up against a wall and shot, the group said.
U.N. observers said the bodies of 13 slain people were discovered about 30 miles east of Deir Ezzor, in the eastern part of the country, on Tuesday night.
The violence drove defiant Syrians to the streets on Friday in what was billed as "a merchants' strike to stop massacring children." A revolt by Syria's merchant class -- which has been an integral part of President Bashar al-Assad's support structure -- could elevate the uprising.
Protesters also hit the streets Friday near the U.N. headquarters in New York, re-enacting horrific scenes from Houla and urging world leaders not to "stand-by idly" as the violence continues.
Despite vows of support from the likes of Putin, Pillay, Hollande and even Syrian leaders, the fate of a peace plan pushed by special U.N.-Arab League envoy Kofi Annan remained uncertain.
Annan, speaking to reporters in Lebanon, said he realized that many had grown impatient with the situation in Syria and are frustrated by the continuing levels of violence. He defended his mission and six-point plan amid criticism that it is serving as "diplomatic cover for more killings."
"This is, I think, one more reason that one should make greater effort to find a solution," he said. "To suggest that an attempt to find a peaceful solution is a reason for further killings -- I find it difficult to defend because the implication is that ... if we were not discussing ways of getting people to the table to discuss political solutions, there would be no killing. I disagree with that."
U.N. Secretary-General Ban Ki-moon said Friday from Turkey that observers, deployed as part of the Annan plan, "are there to help bring about a cease-fire" and "record violations of human rights and also violations of the Annan peace plan." He said they have done a great service, for instance, after the Houla killings by quickly presenting "an authoritative and unbiased account of what happened."
"If the escalating violence shows anything, it is that we urgently need bolder steps," Ban said.
As to what those steps might be, if his peace plan is declared dead, Annan said that's a decision for the U.N. Security Council, which passed a resolution backing the initiative.
"The council and the countries involved will have to keep working together to find a solution," he said. "I am not one of those who believes that there is only one way of solving -- there could be other ways."
CNN's Joe Sterling, Amir Ahmed, Ivan Watson, Holly Yan, Moni Basu and Elizabeth Joseph contributed to this report.