Government warplanes bombed a town in northern Syria on Monday, killing at least 18 people, activists said, while the new UN envoy to the country acknowledged that brokering an end to the nation's civil war will be a "very, very difficult" task.
The Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees said the airstrikes targeted a residential area in the northern town of al-Bab, about 20 miles from the Turkish border. The Observatory said 18 people were killed in the town; the LCC put the death toll at 25.
An amateur video showed men frantically searching for bodies in the rubble of a white building turned into a pile of debris. The video could not be independently verified.
Syrian's uprising began in March 2011 with largely peaceful protests against President Bashar Assad's regime, but has since morphed into a civil war in the face of a brutal government crackdown. Activists say at least 23,000 people have been killed so far.
The violence has escalated in recent months, and activist groups said Sunday that some 5,000 people were killed in August alone - the highest ever reported in more than 17 months of bloodshed.
On Monday, activists reported violence across the country, including the suburbs of the capital Damascus, the eastern region of Deir el-Zour, as well as in Daraa to the south and in Idlib and Aleppo to the north.
Turkey, Saudi Arabia and Qatar are among the harshest critics of President Bashar Assad's regime and strongly support the rebels who are trying to overthrow him.
France's foreign minister has said western powers are preparing a tough response in case Syrian president Bashar Assad's regime deploys chemical or biological weapons in its civil war.
The International Committee of the Red Cross (ICRC) says its new president is heading to Syria on a three-day visit - his first since he took office.
The ICRC said that Peter Maurer will arrive in Syria on Monday and will meet with President Assad and several of his ministers.