The Associated Press reports: Syria’s top diplomat in London said he could no longer represent the regime and defected Monday, as civilians fled the commercial hub of Aleppo in droves amid 10 days of fierce battles between rebels and government forces.

Britain’s Foreign Office said that Khaled al-Ayoubi, the charge d’affaires, told officials that he wasn’t willing to represent the regime any longer, the latest high-profile defection of a diplomat from Syria over the bloody crackdown on the opposition since March 2011.

Fighting is heating up in Aleppo, Syria’s largest city with 3 million people. The U.N. said 200,000 Syrians have left over the past 10 days as the government trains its mortars, tank and helicopter gunships on the neighborhoods seized by the rebels.

“I am extremely concerned by the impact of shelling and use of tanks and other heavy weapons on people in Aleppo,” Valerie Amos, the top U.N. official for humanitarian affairs, said in a statement late Sunday. “Many people have sought temporary shelter in schools and other public buildings in safer areas,” she added. “They urgently need food, mattresses and blankets, hygiene supplies and drinking water.”

Amos said U.N. agencies and the Syrian Red Crescent are working together on supplying those affected by the fighting with blankets and humanitarian supplies, but many remain out of their reach because of the violence.

“It is not known how many people remain trapped in places where fighting continues today,” she warned. Aleppo is Syria’s largest city and commercial hub with about 3 million inhabitants.

Aleppo is some 50 kilometers (30 miles) away from the Turkish border and some of those fleeing the city are headed for Turkey, where tens of thousands of Syrians have already found refuge during the 17-month uprising against authoritarian President Bashar Assad’s rule.