More than 10,000 civilians have fled Sri Lanka's northern war zone over the last two days, an official said Sunday as government forces appear poised to crush the separatist Tamil Tigers, Associated Press reported. The military's relentless offensive in recent months has almost routed the rebels, virtually ending their 25-year war for a separate Tamil nation in the Sinhalese-majority country. The United Nations and aid agencies have expressed concern for the estimated 250,000 civilians trapped in the shrinking sliver of land still controlled by the Tigers. On Sunday, military spokesman Brig. Udaya Nanayakkara said 5,000 civilians fled the war zone for government territory Friday while another 5,600 crossed over Saturday. International organizations including the Red Cross have urged both sides to let the noncombatants out of the conflict zone. The government accuses the rebels of holding civilians as human shields, a charge the rebels deny. The Red Cross said Saturday that some 400 patients are stranded in a makeshift hospital in the north. It urged both sides to allow patients to be evacuated. The United Nations warned Friday of a food crisis in the conflict zone, saying World Food Program stocks in the area were gone. Sri Lanka barred nearly all aid groups from the war zone last year. It does not allow journalists in either, making independent verification of the situation impossible. Some 70,000 people have died in Sri Lanka's civil war, which began in 1983.