United Nations: UN leader Ban Ki-moon expressed concern on Wednesday about the mounting death toll in Syria and called on the government to give "full cooperation" to an Arab League peace plan.

"The secretary general remains extremely concerned about the escalating crisis and the mounting death toll in Syria. As we have said repeatedly, the violence and killings must stop," UN spokesman Martin Nesirky told reporters.

Nesirky said the UN was encouraged by Syria's signature of an accord to let Arab League observers into the country to monitor claims against President Bashar al-Assad's forces.

"Now it is critical for the government of Syria to extend its full cooperation to that mission," the spokesman added.

The UN said last week that more than 5,000 people had been killed in Assad's bloody crackdown on opposition protests, but concerns have been heightened by opposition accounts of more than 200 people killed in the past two days.

The new deaths come as an advance Arab League team prepares to head to Damascus tomorrow to prepare the arrival of about 500 observers.

(Agencies)