Syrian activists say violence across the country Monday killed at least 56 people, as the Arab League's secretary-general called for an international peacekeeping force to be deployed to Syria.

The head of the Britain-based Syrian Observatory for Human Rights told VOA Monday that the heaviest fighting and shelling was in Homs city and in areas of Damascus province. He said two children were among those killed in Douma, an area that Syrian forces have bombarded for days.

The death toll cannot be independently verified.

Meanwhile, Arab League chief Nabil El-Araby said during a visit to Cyprus that an international peacekeeping force should be deployed to Syria to “impose a cease-fire” without getting involved in the fighting.

He said a meeting between the Russian and U.S. leaders on the sidelines of the G-20 meeting in Mexico will be the “most important” event in enlisting “outside support” for efforts to end the conflict in Syria “in a way that will give the Syrian people the right to attain their legitimate demands.”

U.S. President Barack Obama and Russian President Vladimir Putin are expected to discuss the Syrian conflict during Monday's meeting.

Russia is a longtime ally of Syria and has shielded President Bashar al-Assad from U.N. sanctions sought by Western and Arab powers who oppose his 11-year rule.

The escalating violence forced some 300 unarmed U.N. observers to suspend their monitoring mission Saturday. But the head of the observer mission, Major General Robert Mood, said his staff will not leave the country.

On Sunday, a group of U.N. observers travelled from Damascus to replace colleagues in Hama.

The U.N. sent its observers to Syria to monitor the implementation of a six-point peace plan and cease-fire brokered by international envoy Kofi Annan. But the cease-fire never took hold and a group of observers came under attack last week when they went to visit the town of al-Haffeh in Latakia.

Syrian opposition officials in Istanbul, including the Syrian National Council's Bassam Imadi, said recently they believe the U.N. mission has failed.

The U.N. Security Council must decide whether to renew the mission by July 15.