Russia said on Thursday it was very concerned about reports of an Israeli air attack deep inside Syria near Damascus and that any such action, if confirmed, would amount to unacceptable military interference in the war-ravaged country.

"If this information is confirmed, then we are dealing with unprovoked attacks on targets on the territory of a sovereign country, which blatantly violates the UN charter and is unacceptable, no matter the motives to justify it," the Russian Foreign Ministry said in a statement.

Free Syrian Army fighters run for cover as a tank shell explodes on a wall during heavy fighting in the Ain Tarma neighborhood of Damascus on Wednesday. [Photo/Agencies]

Russia added that it was taking "urgent measures" to clarify the situation. "We once again call for the end to all violence in Syria, underscoring the inadmissibility of any type of intervention from abroad, and the start of inter-Syrian dialogue based on the Geneva agreements of June 30, 2012," the Russian statement said.

Details of the strike remain sketchy and, in parts, contradictory. Syria said Israeli warplanes, flying low to avoid detection by radar, crossed into its airspace from Lebanon and struck the Jamraya military research center in the suburbs of Damascus.

But diplomats, Syrian rebels and regional security sources said the planes hit a weapons convoy heading from Syria to Lebanon, apparently destined for President Bashar al-Assad's ally Hezbollah, and the rebels said they - not Israel - hit Jamraya with mortars.

Israeli newspapers on Thursday quoted foreign media for reports on the strike. Journalists in Israel are required to submit articles on security and military issues to the censor, which has the power to block any publication of material it deems could compromise state security.

The force of the dawn attack shook the ground, waking nearby residents with up to a dozen blasts, said one source in the area.

"We were sleeping. Then we started hearing rockets hitting the complex and the ground started shaking and we ran into the basement," said a woman who lives adjacent to the sprawling Jamraya site. She declined to be named because of the sensitivity.

Chinese Foreign Ministry spokesman Hong Lei on Thursday urged maintaining regional peace and stability following the reported airstrike.

Hong said that China hopes relevant parties will avoid making any moves that may escalate the current tension in Syria.

UN-Arab League crisis envoy Lakhdar Brahimi has shuttled between world capitals in recent weeks trying to push the Geneva accord.

But Brahimi told the Security Council this week that the pact could not be saved in its current form and needed to be altered.

"I'm not calling on the Security Council to take action because the Geneva declaration that contains, indeed, a lot of elements that would provide for a reasonable solution to the conflict cannot be implemented as it stands," Brahimi told the Security Council.

"It needs action from the council, and I have suggested a few ideas to them."

AFP-Reuters-Xinhua