Annan optimistic of cease-fire amid new shelling in Syria International envoy Kofi Annan says a cease-fire can still be reached by Thursday A peace plan he brokered calls for the government and the opposition to lay down their weapons by that day Syria's self-imposed deadline to pull back government forces came and went Tuesday "It is extremely important that we find a way to end the violence in Syria," he says (CNN) -- Shelling and rocket fire erupted in Syria on Wednesday as international envoy Kofi Annan held out hope that government forces and the opposition will meet a looming deadline to end all hostilities. Annan said a cease-fire can still be reached by Thursday, when a peace plan he brokered calls for the government and the opposition to lay down their weapons. The deadline expires at 6 a.m. Syrian time (11 p.m. ET Wednesday). Syria's self-imposed deadline to pull back government forces came and went Tuesday as attacks continued nationwide, sparking condemnation against the regime. "We have agreed that we need to find a peaceful solution to the crisis," Annan said Wednesday. It is extremely important that we find a way to end the violence and crisis going on in Syria. Syrian troops pounded cities nationwide Tuesday, killing at least 101 people, opposition activists said. But Annan said he remained optimistic about the peace plan as he called on the parties to honor it. "If you want to take it off the table, what would you replace it with?" he asked. Let me once again appeal to the Syrian government, to all the parties, to cease violence according to the plan. The Syrian government said this week it had taken steps to ease back, but Annan countered that while government forces had moved out of some areas, they had relocated into others that have not been previously targeted. "Several new localities appear to have been subject to military operations, including the use of heavy weapons on population centers," he said. Regime and rebel fighters both refuse to back down as sporadic mortar shelling and rocket fire continued early Wednesday in the Homs neighborhoods, opposition activists said. "Military planes have been hovering over Homs skies since the early hours," said Saif al-Arab, a Homs resident . And some shelling already started today. Usually planes fly for a while looking for what they perceive as targets then the shelling follows. Syrian activists had angry words for Annan, saying the peace process was giving the regime more time to kill. During his visit to refugee camps in Turkey, refugees frustrated with the peace process yelled "liar, liar!" at Annan, according to camp resident Mohamed El Abd. More than 24,000 Syrians have crossed the border. Al-Assad's regime had agreed to the deadline, but demanded that its opponents, whom it calls armed terrorists, put down their weapons. It also wanted a promise from foreign governments not to fund opposition groups. "The political process that emerges must be Syrian-led and should respect the aspirations of the Syrian people," he said. " But what's important is that the governments in the region and beyond work together with the Syrians to resolve this current crisis. This is a region that has seen many tensions and many shocks, and I don't think it can afford another shock. Syrians' anti-government protests started in March 2011, followed by a violent crackdown by the regime. The Local Coordination Committees of Syria puts the toll at more than 11,000.