MOSCOW, Feb. 23 (Xinhua) -- Russian Foreign Minister Sergei Lavrov on Friday accused the U.S.-led coalition in Syria of failing to fight the Nusra Front terrorists that Russia deems as the major obstacle to reaching a cease-fire in the Mideast country.

"The Nusra Front is not being targeted. We still have no evidence that the U.S.-led coalition considers the Nusra Front as a target for its military campaign," Lavrov was quoted as saying by Russia's Sputnik news agency.

The Nusra Front terrorist group in the besieged Eastern Ghouta on the outskirts of Syria's capital Damascus used civilians as human shields during fighting in order to put the blame for civilian casualties on the Syrian government and its allies, Lavrov told a news conference after a meeting with his Uzbek counterpart, Abdulaziz Kamilov.

The Russian foreign minister made the remarks when reports of heavy civilian casualties and hospital attacks in the latest escalation of violence in Eastern Ghouta have prompted calls from countries for a 30-day humanitarian cease-fire across Syria to enable medical aid and evacuations.

The United Nations Security Council began Thursday to consider a resolution demanding such a cease-fire, drafted by Kuwait and Sweden.

On the worsening situation in the last rebel enclave near Damascus, Russia said Nusra Front terrorists have repeatedly launched attacks on Damascus, provoking mounting retaliations from the Syrian government side, especially intensive airstrikes and shellings in recent days.

Stressing a guarantee was needed for the terrorists to lay down their weapons, Lavrov said Russia is ready to back an amended cease-fire proposal.

"In order to make this resolution effective -- and we are ready to agree on a document that will do so -- we propose a formula that will make the cease-fire real and based on the guarantees of the parties that are currently residing in East Ghouta," he said.

"The guarantees should be backed by the external powers," he added.