DAMASCUS (Agencies) - Security forces killed at least 12 civilians on Friday, including two children, on the eve of an Arab League deadline for Syria to stop its lethal crackdown on protesters. The latest bloodletting came as Turkey warned of the risk of civil war and as thousands of protesters took to the streets to urge nations to expel Syrian ambassadors, in defiance of massive security force deployments. Russian Prime Minister Vladimir Putin called for restraint over the Syrian crisis, after talks with his French counterpart who accused President Bashar al-Assad of being deaf to pressure. "We are calling for restraint and caution. This is our position," Putin told a Moscow news conference, the day after his foreign minister had likened the situation in Syria to a civil war. Turkey said the risk of civil war was real -- a warning also echoed by analysts monitoring developments in Syria amid growing losses among regular army troops at the hands of mutinous soldiers. The Arab League said it was examining a Syrian request to make changes to a proposal to send 500 observers to Damascus to help implement a peace plan agreed earlier this month. Facing growing isolation, Syria has been told by its Arab peers to stop the lethal repression against protesters by 2200 GMT on Saturday or risk sanctions, and the Arab League has voted to expel it from the 22-member bloc. Iran said the suspension call was "a historic mistake" and would in itself cause civil war. "The path the Arab League has taken is completely about defeating Syria from inside, and triggering a civil war," Alaaddin Boroujerdi, the head of the Iranian parliamentary commission on foreign policy, said on a visit to Turkey. The repression against protests that erupted in mid-March has claimed more than 3,500 lives so far, according to UN estimates.