BEIRUT - Syrian tanks shelled the central city of Hama in the early hours of Tuesday morning, an activist said, and tanks continued to patrol the streets on the day Syrian President Bashar Assad has agreed to start withdrawing government forces from urban areas."At 2 a.m. we heard two shells fall and the sound of tanks moving around the streets," said Manhal Abu Bakr, an activist and citizen journalist.Failure to end the violence would turn attention back to the diplomatic stalemate that has left Western and Arab powers on the one hand and Assad's friends in Russia, China and Iran on the other all calling for calm. But they are sharply at odds over how that might be achieved and how Syria would be governed from then on.Syrian FM in Moscow for talksSyrian Foreign Minister Walid Mouallem was in Moscow for talks on Tuesday with his Russian counterpart Sergei Lavrov. One of Lavrov's deputies said Russia was working with the Syrian authorities to promote talks with the opposition. But he reiterated Moscow's vocal opposition to foreign intervention.There was also no sign the rebels were holding fire.Opposition activists, denounced by Assad and his aides as foreign-backed terrorists, said their lightly armed and scattered forces had mounted fatal attacks on troops. They accused government forces of bombarding villages around Idlib in the northwest, as well as attacks elsewhere in the country of 22 million.Among the forces ranged against Assad and hoping, with Western blessing, to end his family's four-decade rule there was more talk of war than of peace. One general who defected to the rebels demanded foreign air strikes on the artillery and tank units that are the spearhead of the Assad government's response to calls for change inspired by last year's Arab uprisings.70% of Syrian military is out of action"You will not need a long air campaign. Seventy percent of the Syrian military is already out of action and air strikes would be a message to the Syrian people that the international community is really with them," Mustafa al-Sheikh told Reuters at a camp where Turkey is giving refuge to Syrian army officers.Saying Assad could not rely on conscript troops from the Sunni Muslim majority to follow orders from an officer corps dominated by members of the president's minority Alawite sect, the general urged the United States, Turkey and Arab states to mount the kind of strikes used against Yugoslavia in the 1990s. The aim would be to create safe areas for Syrian army deserters to gather.Such talk among the fractious rebel movements, like calls from others for more weaponry to be smuggled in to opposition groups on the ground, has fallen on deaf ears."There is no gunfire now. They shell us at night so that it is hard to film," he said over Skype. Internet video footage, which Abu Bakr said was filmed in Hama overnight, showed nighttime explosions in a built-up area.In Douma, a suburb of the capital Damascus, another activist said tanks were still in the streets on Tuesday morning. Diplomats trying to contain a crisis that has inflamed the Middle East and pitched old Cold War rivals into opposing camps will not wish to abandon their most comprehensive peace plan yet. The plan's author, international envoy Kofi Annan, visits Turkey and Iran on Tuesday, while Russia hosts the Syrian foreign minister.In Damascus, Syrian President Bashar Assad said nothing on Monday about whether he would honor his undertaking to Annan to start withdrawing government forces from urban areas on April 10 - a deadline that diplomats say appears to give him until midnight Syrian time, or 2100 GMT, on Tuesday to comply.Assad's demand on Sunday for written guarantees of good faith from the rebels - which their leaders rejected out of hand - as well as the hostile actions of Syrian troops on the ground, fueled doubts that Annan's schedule for the full truce to start by 6 a.m. (0300 GMT) on Thursday, April 12, would be respected.Syria was to have started pulling troops out of towns and cities by Tuesday to pave the way for a ceasefire to start 48 hours later."April 10 has become void," concluded Turkish Deputy Foreign Minister Naci Koru. Ankara, Assad's former ally and now a foe, deplored shooting that wounded five people in a refugee camp inside Turkey - in the border area which Annan, the former UN secretary-general, is expected to visit on Tuesday.Another neighbor, Lebanon, condemned the killing of a local journalist by Syrian soldiers firing over the border.In Washington, State Department spokeswoman Victoria Nuland said: "These incidents are just another indication that the Assad regime does not seem at all willing to meet the commitments that it made to Kofi Annan."She derided Assad's new condition for a truce as "chaff" to "stall for time" and said there was "no indication" of his forces preparing to withdraw.Opposition activists in Idlib province, near the Turkish border, accused troops of mounting an offensive that had killed dozens this week, including young men rounded up and executed. Other anti-Assad groups said the army shelled a village near the central city of Hama, killing 30 people, including women and children."The world gave Assad a deadline," said activist Mohammad Abdallah. "But he sees it as an opportunity."The United Nations says Syrian forces have killed 9,000 people in 13 months, while Assad's government says rebels have killed more than 3,000 soldiers and security personnel.Government curbs on the media limit independent reporting from inside Syria.UN Secretary-General Ban Ki-moon was "alarmed by the reports of continued violence and human rights violations in Syria, which resulted in an increased flow of refugees into neighboring countries," his office said on Monday. "The timeline for the complete cessation of violence endorsed by the Security Council must be respected by all without condition."