Five unarmed UN monitors toured Homs, the battered city at the heart of the Syrian uprising, on foot on Saturday, The Associated Press reported.

The report noted the monitors encountered unusually calm streets after weeks of shelling.

The observers, members of an eight-member advance team that has been on the ground in Syria for a week, were seen on amateur video Saturday walking through rubble-strewn deserted streets lined by gutted apartment buildings.

Activists reported only sporadic gunfire, but no shelling, and said troops had pulled armored vehicles off the streets prior to the visit. Two observers stayed behind in Homs to keep monitoring the city, after the rest of the team left Saturday evening, AP noted.

The mission is meant to shore up a ceasefire that officially took effect ten days ago, but has failed to halt violence. UN chief Ban Ki-moon has accused Syrian President Bashar Assad of violating the truce, and was quoted by AP as having said Saturday that “the gross violations of the fundamental rights of the Syrian people must stop at once.”

Meanwhile on Saturday, the United Nations Security Council approved the expansion of the UN ceasefire observer force in Syria from 30 to 300. The council also demanded an “immediate halt to the violence.”

The resolution is the first authorizing unarmed UN military observers to go into a conflict area, giving Secretary-General Ban Ki-moon authority to decide when to deploy the additional monitors.

U.S. Ambassador to the UN, Susan Rice, warned that if Assad doesn’t make good on all commitments or obstructs the monitors’ work, the United States would pursue other “measures.”

“Let there be no doubt. We, our allies and others in this body are planning and preparing for those actions that will be required of all of us if the Assad regime persists in the slaughter of the Syrian people,” AP quoted Rice as having said. She added the U.S. will not wait 90 days to take these measures if Syria keeps flouting its obligations.

On Friday there had been a disagreement among members of the Security Council regarding the resolution. European nations and Russia proposed rival UN resolutions, with both calling for expanding the number of UN monitors in, but disagreeing on possible sanctions and on how quickly the larger observer force should get on the ground.

At least 18 Syrian security forces were killed in a series of attacks on Friday. In addition, local human rights groups reported that 13 civilians were killed across the country.