At least 28 civilians have been killed in two days of fighting as Sri Lankan troops try to push into a small "no-fire zone" where Tamil Tiger rebels have bunkered down for their final stand, a health official said Saturday. The rebels lost to government forces the de facto state they controlled for years in parts of the country's north and east and have retreated into a tiny slice of land that the government earlier declared a haven for civilians fleeing the fighting in this island nation's 25-year civil war. There have been widespread international calls for a cease-fire to allow the more than 100,000 civilians trapped in the 20-square kilometers zone to reach safety - but the government has rejected a long-term cease-fire, saying it would only give the rebels time to regroup. An official from the only makeshift hospital in the region said 15 civilians bodies with war wounds were brought to his facility Saturday and another 13 bodies the day before. More than 160 civilians are being treated for wounds after being caught in the crossfire between the military and rebels, he said.