Syria\'s military intensified its northern offensive Thursday after all but overtaking the city of Idlib, the second opposition stronghold besieged in two weeks. At the same time, U.N.-Arab League Joint Special Envoy for Syria Kofi Annan, seeking to end the yearlong bloodshed, said he received a communication from aides to President Bashar Assad asking for clarification of the proposals Annan made in Damascus meetings during the weekend. \"But given the grave and tragic situation on the ground, everyone must realize that time is of the essence,\" spokesman Ahmad Fawzi said in a statement from Geneva, Switzerland. \"This crisis cannot be allowed to drag on,\" he said. An Arab diplomat told The Wall Street Journal the Assad regime\'s response was \"not a definitive no,\" but argued over wording, similar to a process last year, when Damascus quarreled over language and terms of an Arab League peace plan. The regime approved the plan in November after a six-week delay. Annan is due to brief the U.N. Security Council Friday. Activists in Syria said the forces loyal to Assad drove rebel fighters and hundreds of residents out of Idlib, near Turkey. Regime forces bombarded the city using tanks, helicopters and artillery, rockets and mortars, opposition groups said, pointing out the approach was similar to that which overwhelmed the Baba Amr neighborhood of Homs two weeks ago. Between 16 and 45 people, including children, were killed in the government assault, opposition groups said. The death toll could not be independently verified because the regime does not permit journalists into the area. Syria sent an estimated 130 tanks and armored vehicles, along with busloads of security forces, to the rebellious southern city of Daraa, the starting point of the uprising a year ago, activists said. Unlike opposition cities elsewhere, Daraa lacks a strong presence of the opposition Free Syrian Army, The New York Times reported. Rebels have not held entire neighborhoods in Daraa, as they did further north, the newspaper said. \"It seems they want to have a situation similar to Idlib and Homs,\" activist Anwar Fares told the Times. Protests in Daraa March 15, 2011, expanded into the nationwide uprising that has become the most deadly of the Arab revolts. The protest a year ago followed the arrest of 15 schoolchildren, ages 9 to 15, from the same family who had scrawled anti-regime graffiti on the wall of their school. Attempts to negotiate the children\'s release were rejected by the local government, so a few hundred protesters gathered in front of a mosque, calling for reforms and an end of corruption. The gathering quickly increased in size to more than 3,000 people. Syrian security forces opened fire on the protesters, killing four people.