BEIRUT - The Syrian army killed more than 20 people in Hama on Monday, activists said, shattering a week of relative quiet in the central city visited a day earlier by UN monitors laying the ground for a wider mission to oversee a shaky 11-day ceasefire.
A small group of unarmed observers has been in Syria for a week, tracking the truce between forces loyal to President Bashar Assad and opponents inspired by 'Arab Spring' uprisings in North Africa and elsewhere in the Middle East.
The deal has curbed some of the violence, but the latest killings in Hama's Arbaeen district have laid bare the difficulty of bringing to a complete halt 13 months of fighting in which more than 9,000 people have died.
The UN Security Council has approved an expansion of the monitoring mission to 300 observers, although Assad's opponents say such numbers are fat too small to keep a track on events in a nation of 23 million.
The UN political affairs chief said on Monday that the fighting in Syria was continuing despite announcements from the government that it will comply with the truce and has withdrawn troops and heavy weapons from population centers.
"The cessation of armed violence remains incomplete," Lynn Pascoe, UN undersecretary-general for political affairs, told the Security Council during a debate on the Middle East.
There was no immediate comment from Syrian authorities, who say they are committed to international mediator Kofi Annan's April 12 ceasefire agreement, but reserve the right to respond to what they say are continued attacks by "terrorist groups".
A local activist called Mousab told Reuters by telephone in neighboring Lebanon that military forces entered the Hama district "and shot people in the street".
"It began in the morning with tanks and artillery. There were houses burning," he said, adding that at least 20 people were killed, 60 were wounded and more could be buried under collapsed buildings.
The British-based Syrian Observatory for Human Rights said it had the names of 28 people killed in Hama on Monday.
A group of UN monitors visited Hama on Sunday, and activists said soldiers opened fire to prevent a crowd from meeting them in the main square of the city, which had been relatively quiet since the ceasefire agreement.
Hama is a hotbed of anti-Assad sentiment where thousands of people were killed 30 years ago in a crackdown on an armed Islamist uprising by his father, Hafez.