Syrian government troops shelled suburbs of the capital Damascus, killing at least 12 people in a stepped-up regime offensive on rebel areas around the country, the Associated Press reported.


Most of the deaths occurred overnight in the restive suburb of Douma, where activists said regime forces fired mortars that struck a residential building, killing eight people.


In the central city of Homs, government troops kept up their relentless shelling of rebel-held districts, including Khaldiyeh and Jouret el-Shayyah, in an effort to recover those territories.


The Britain-based Syrian Observatory for Human Rights urged UN Secretary General Ban Ki-moon to "intervene immediately."


In a statement, the Observatory said more than 1,000 families, including women and children, were trapped in embattled districts amid worsening humanitarian conditions and called for the evacuation and protection of dozens of wounded whose lives were in danger because of the scarcity of doctors and medicines needed to treat them.


Douma-based activist Mohammed Saeed and the Observatory, which relies on a network of activists on the ground, said that four people were killed in the shelling of Arbeen and Tall suburbs.


"The regime is trying to purge the suburbs of the capital of all resistance," Saeed said. He said the fire on the suburbs was indiscriminate and that a man, his wife and their child died when a mortar shell hit their apartment in Arbeen.


State-run news agency SANA said troops stormed hideouts of armed groups in Douma and killed and wounded a number of "terrorists." The Syrian government often refers to rebels as terrorists and armed gangs. It also said troops foiled an overnight infiltration attempt by armed groups from Lebanon into Syria and wounded and killed a number of terrorists.


Saeed said UN observers deployed in Syria to monitor the cease-fire, which never really took hold, have not been to Douma in over a week. "But anyway, all they can do is record what they see, they cannot help," he said.


There are nearly 300 monitors currently in Syria to follow up on a peace plan brokered by special international envoy Kofi Annan, which now seems to be disintegrating. The regime and the opposition have ignored the cease-fire, which was supposed to go into effect April 12, and the recent escalation is raising questions about how effective the unarmed monitors can be in a conflict that every day looks more like a civil war.