AMMAN - Protests against President Bashar Assad erupted in several Syrian cities on Friday, activists said, and the Arab League chief said he feared the bloody unrest could degenerate into a civil war with ill effects for the wider region.Security forces killed one demonstrator in the northwestern town of Idlib, the Syrian Observatory for Human Rights said.RELATED:Syrians use noise to protest through the nightUN chief visits Lebanon as Syria revolt seethesProtests also flared after Friday prayers in some areas of the capital Damascus, as well as the port city of Latakia, where Arab League monitors had come under attack from a pro-Assad crowd on Monday. "The people want the downfall of the regime!" people chanted near a Latakia mosque, one activist said. Syrians determined to end four decades of Assad family rule have kept up protests since March despite a fierce crackdown by Assad's military and security forces that the United Nations says has cost more than 5,000 lives.Some, including army deserters, have taken up arms in recent months. Syrian authorities say foreign-backed "terrorists" have killed 2,000 soldiers and police since the revolt began.The most senior Syrian officer to defect to the opposition told Reuters that desertions were wearing down the army, but that rebels could take more than a year to topple Assad.General Mostafa Ahmad al-Sheikh said that up to 20,000 soldiers, mostly majority Sunni Muslims, had left despite "iron controls," although most were more focused on evading capture by the secret police than on fighting the security forces. The revolt is likely to take longer than those that toppled the autocratic rulers of Libya, Egypt and Tunisia because Assad retains the loyalty of highly trained and well equipped forces from his minority Alawite sect, Sheikh said."If we get 25,000 to 30,000 deserters mounting guerrilla warfare in small groups of six or seven it is enough to exhaust the army in a year to a year-and-a-half, even if they are armed only with rocket-propelled grenades and light weapons," he said in a telephone interview from south Turkey on Thursday.Video footage posted on the Internet on Friday showed the burning hulk of an armored personnel carrier on a street in Homs, a hotbed of protests and armed resistance to Assad. A voice on the clip said the Free Syrian Army mounted the attack.Violent clashes raise fear of civil warArmed clashes, now punctuating what began as a non-violent protest movement, have raised fears of a full-scale conflict in Syria, which also has Christian and Kurdish minorities."Yes I fear a civil war and the events that we see and hear about now could lead to a civil war," said Nabil Elaraby, head of the Arab League, which deployed monitors on Dec. 26 to check whether Syria was respecting an Arab peace plan."Any problems in Syria will have consequences for the neighboring states," he told Egypt's Al-Hayat television.Syria, which borders Lebanon, Turkey, Iraq, Jordan and Israel, is at the heart of a conflict-prone Middle East, where its closest allies are Iran and the Lebanese Hezbollah group. Elaraby described reports from the chief of the monitoring mission as "worrying", but said there was "no doubt that the pace of killing has fallen with the presence of the observers".That contradicts the view of a senior UN official who told the Security Council this week that the rate of killings had accelerated to about 40 a day since the Arab monitors arrived, according to Washington's ambassador to the world body.The British-based Observatory said at least 21 people were killed on Thursday, including seven in the eastern city of Deir al-Zor and seven security force members in Maarat al-Noman.