Heavy clashes erupted Monday between opposition rebels and Syrian regular army units near the Turkish-Syrian border, as the first batch of a UN advance team were due to start observing the shaky ceasefire in the country, activists said, according to DPA. "Fierce clashes are taking place in the northern city of Idlib, while shelling resumed on areas in Homs, amid attempts by government forces to take control of some areas inside the central city," London-based Syrian observatory for Human Rights said in a statement.