Syria on Monday rejected the Arab League's wide-ranging new plan to end the country's 10-month crisis, saying the League's call for a national unity government in two months is a clear violation of Syrian sovereignty, as violence raged.

Tens of thousands of people poured into the streets in a suburb outside the capital Damascus to mourn 11 residents who were either shot dead by security forces or killed in clashes between army defectors and troops a day earlier, activists said.

An activist group said as many as 23 people were killed in Syria on Monday.

The crowd in Douma — which one activist said was 60,000-strong — was under the protection of dozens of army defectors who are in control of the area after regime forces pulled out late Sunday, said Samer al-Omar, a Douma resident.

The reports could not be independently confirmed.

President Bashar Assad blames the uprising that erupted in March on terrorists and armed gangs acting out a foreign conspiracy to destabilize the country. His regime has retaliated with a brutal crackdown that the UN says has killed more than 5,400 people.

There is growing urgency, however, to find a resolution to a crisis that is growing increasingly violent as regime opponents and army defectors who have switched sides have started to fight back against government forces.

The Arab League has tried to stem the bloodshed by condemning the crackdown, imposing sanctions and sending a team of observers to the country. On Sunday, the League called for a unity government within two months, which would then prepare for parliamentary and presidential elections to be held under Arab and international supervision.

The proposal also provides for Assad to give his vice-president full powers to co-operate with the proposed government to enable it to carry out its duties during a transitional period.

EU extends sanctions

The state-run news agency, SANA, said Damascus considers the plan "flagrant interference in its internal affairs" and the latest turn in an international plot against Syria.

It was not immediately clear what steps, if any, Syria could take to counter the Arab League's stance.

In Washington, State Department spokeswoman Victoria Nuland said it was regrettable that Assad rejected the League's transition proposal "almost before the ink was dry."

"This just speaks again to the fact that he's thinking about himself and his cronies, not about his people," Nuland told a news briefing on Monday.

The European Union backed the Arab plan Monday, and it extended existing sanctions against Assad's government by adding 22 more officials and eight companies to its blacklist.

In New York, German UN Ambassador Peter Wittig called Monday on fellow Security Council members to endorse the Arab League's new plan to end the violence in Syria, including formation of a national unity government.

"The decisions taken in Cairo may be a game-changer, also for the Security Council," Wittig told a small group of reporters.

League defends observer mission

Syria appeared to get a serious boost Monday from Russia after business daily Kommersant reported that Moscow has signed a contract to sell 36 Yak-130 combat jets to Syria — a deal that, if confirmed, would openly defy international efforts to pressure Assad's regime.

The Arab League's observer mission has come under heavy criticism for failing to stop the violence in Syria.

On Monday, the head of the mission defended the observers' work, saying their presence had cut down on the bloodshed. Speaking at League headquarters in Cairo, Sudanese Gen. Mohammed Ahmed al-Dabi told reporters the observers have witnessed violence from both the Syrian security forces and armed opposition groups.

"When the delegation arrived, there was clear and obvious violence," he said. "But after the delegation arrived, the violence started to lessen gradually."

On Sunday, Arab League foreign ministers extended the mission for another month. The mission's one-month mandate technically expired on Thursday.