BEIRUT - Overnight clashes between security forces and army defectors in northern Syria left 12 soldiers and defectors and three civilians dead early on Saturday, activists said.Fighting has become more intense as rebels increasingly often confront security forces loyal to President Bashar al-Assad who are trying to suppress the eight-month-old protest movement against his rule.RELATED:Analysis: Arab sanctions close net on Syria tradeUN: Syria in civil war, death toll at 4,000The Syrian Observatory for Human Rights said fighting broke out around midnight in the northern city of Idlib, near the Turkish border."Seven were killed from the army and regime security forces, including an army officer," the group said. "Three civilians and five defectors were also killed."More than 4,000 people have died since protests broke out in March against the Assad family's 41-year rule, according to the United Nations, which says the violence in Syria looks like civil war.Syria faces mounting international and regional isolation as organizations such as the Arab League and the European Union, and the United States, demand that Damascus stop the bloodshed and talk to its opponents, and impose increasingly tough sanctions when it does not do so. Syrian authorities say they are fighting foreign-backed "terrorist groups" trying to spark civil war who have killed some 1,100 soldiers and police since March.The head of the main group of army deserters who have joined the opposition, the Free Syrian Army, told Reuters that his forces were switching their tactics from seizing equipment and hitting security checkpoints to attacking the military directly.He said this was a necessary response to an increasing use of violence in Damascus' military crackdown on protests.On Friday, the United Nations top human rights forum strongly condemned Syria for "gross and systematic" violations by its forces, including executions, that it said may amount to crimes against humanity.The 47-member forum adopted a resolution put forward by the European Union (EU) by a vote of 37 states in favor, four against including China and Russia, with six abstentions. The text called for the "main bodies" of the United Nations to consider a UN report which found that crimes of humanity had been committed and "take appropriate action."