BEIRUT – Syrian troops fired tear gas and bullets on thousands of protesters who spilled out of mosques after noon prayers Friday, activists said.

State media reported that bombs and shootings killed 17 soldiers as the latest diplomatic efforts failed to halt more than 13 months of bloodshed.

Opposition activists reported that at least 11 Syrian civilians were killed in regime shelling and other attacks Friday, the main day of the week for protests calling for the ouster of President Bashar Assad.

The United Nations hopes to have 30 observers in Syria next week to monitor the tenuous cease-fire between regime troops and opposition, and plans are being made for the deployment of up to a total of 300. An advance team of seven monitors, whose presence set off anti-Assad marches that prompted gunfire from security forces in at least two areas earlier this week, did not venture out Friday.

The U.N. is also trying to ramp up its humanitarian response and send more food, medicine and aid workers to Syria, said John Ging, the head of emergency response at the U.N.’s Office for the Coordination of Humanitarian Affairs.

“The whole infrastructure of the country is under strain,” Ging said. He added that the Syrian regime has finally acknowledged that there is a “serious humanitarian need” and that he hopes this will ease the aid mission.

U.N. deputy spokesman Eduardo del Buey said the World Food Program, through the Syrian Red Crescent, had given food to about 100,000 Syrians in need, a figure expected to double in a month.

The U.N. estimates some 230,000 Syrians have been displaced and more than 9,000 killed since the uprising against Assad erupted more than a year ago. The revolt began with largely peaceful protests, but has grown increasingly violent as the opposition has taken up arms in response to a brutal regime crackdown.

A U.N.-brokered cease-fire that went into effect last week has been steadily unraveling, with regime forces continuing to shell rebel-held neighborhoods in the central city of Homs and opposition fighters ambushing government troops.

Western powers have called for Assad’s ouster, but the Syrian leader has dug in, unleashing his military on an ill-equipped and fractured opposition, and there appears to be little appetite in the international community to try to dislodge him by force with an operation similar to the one that helped topple Libyan leader Moammar Gadhafi last year.