BAGHDAD - United Nations Secretary General Ban Ki-moon said Thursday that Syrian President Bashar Assad must turn his acceptance of a six-point peace plan into action to divert his country from a "dangerous trajectory" with risks for the entire region."It essential that President Assad put those commitments into immediate effect. The world is waiting for commitments to be translated into action. The key here is implementation, there is no time to waste," Ban told an Arab League Summit in Baghdad on Thursday. Fighting between Syrian security forces and rebels killed at least 13 people on Thursday as Arab leaders gathered.Arab leaders, who appear to have backed away from their call on Assad to step aside and hand power over to a deputy, remain split over how to deal with the continuing violence.Meanwhile, a rocket or mortar round landed on the edge of the fortified Green Zone in Iraq's capital on Thursday, where the Arab League summit was taking place, a senior security source said.There were no immediate reports of casualties or damage. A Reuters reporter at the scene also heard the blast. Pre-empting the summit, Syria said on Wednesday it would reject any initiatives from the Arab League, which suspended Syria in November, and said it would deal only with individual Arab states.In Istanbul, Syrian opposition representatives met to try to settle deep internal disputes before the arrival of Western foreign ministers for a "Friends of Syria" conference on Sunday to map out where the year-old uprising is heading.The opposition Syrian Observatory for Human Rights, which monitors the violence, reported that eight members of the security forces were wounded in a clash with armed defectors in Dael, in the southern province of Deraa.In the town of Kherbet Ghazaleh, surrounded by the army and security forces, loud explosions were heard. In northern Hama province, an army convoy was ambushed and two soldiers killed. In Idlib province three people died when the army launched a raid in a rural area east of the town of Maarat al-Nuaman.The Observatory reported clashes between army and defectors near the town of Zabadani, near the Lebanese border. In rural Damascus province explosions were heard and smoke was seen rising from building in the town of Harasta.Syria's state news agency SANA said that two colonels were assassinated in the northern city of Aleppo on Thursday. "Four terrorists shot Abdul Karim al-Rai and Fuad Shaaban ... while they were on their way to work," SANA said.US State Department spokeswoman Victoria Nuland said on Wednesday that Assad "has not taken the necessary steps to implement" the peace plan of former UN Secretary General Kofi Annan, now special Syria envoy for the UN and Arab League.