By Stephanie Nebehay

GENEVA | Wed Jun 15, 2011 7:50am EDT

(Reuters) – The U.N. human rights office said on Wednesday that Syrian security forces have repressed pro-democracy protests through executions, mass arrests and torture, citing widespread allegations it has received.

Entire towns have been besieged, including Deraa, preventing civilians from fleeing and depriving many of food supplies and access to medical care, especially the wounded, it said.