Photo: The Canadian Press

Syrian Foreign Minister Walid al-Moallem sits beneath a portrait of Syrian President Bashar Assad as he speaks during a press conference in Damascus, Syria.

Syria's foreign minister said Monday that an internationally-brokered cease-fire is still viable, as rescue workers in Aleppo sifted through the rubble from the heaviest airstrikes on rebel-held areas of the northern city in five years.

Foreign Minister Walid al-Moallem, speaking to Mayadeen TV from New York, also said the government is prepared to take part in a unity government incorporating elements from the opposition, an offer that has been rejected in the past.

Opposition activists say more than 200 civilians have been killed in the past week under a sustained aerial campaign that U.N. envoy Staffan de Mistura called one of the worst of the 5 1/2-year war. The U.N. Security Council convened an emergency meeting but failed to take any action because of deep divisions between Russia and Western powers.

"What Russia is sponsoring and doing is not counterterrorism, it's barbarism," said U.S. Ambassador Samantha Power. "It's apocalyptic what is being done in eastern Aleppo."

Airstrikes on Aleppo on Monday killed at least six people, according to the Local Coordination Committees, an activist-run collective. The Britain-based Syrian Observatory for Human Rights reported hours later that 12 were killed, including three children.

Al-Moallem accused the U.S., Britain, and France of convening the Security Council meeting a day earlier in order to support "terrorists" inside Syria. But he said ongoing communications between U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov meant a truce agreement brokered two weeks ago is "not dead."

Syria's military declared the cease-fire ended one week ago.

The spokesman for Russian President Vladimir Putin said the cease-fire is ineffective, but that Moscow is not losing hope for a political solution to the country's crisis.

U.S. Secretary of State John Kerry said the Syrian and Russian governments "seem intent on taking Aleppo and destroying it in the process."