UN Secretary General Ban Ki-moon on Tuesday called on Sri Lankan leaders to call off the fighting so humanitarian assistance can reach civilians trapped by the conflict, according to dpa. Ban said he spoke to Sri Lankan President Mahinda Rajapaksa early Tuesday to request a "humanitarian pause in the fighting." "This would allow more desperately needed aid, above all food and medicines, to get in," he said. "It will allow the UN to have access to the conflict zone to assess the situation properly. It will save lives." He said government authorities should avoid use of artillery and heavy weaponry against areas where civilians are taking refuge from the fighting between government forces and the Liberation Tigers of Tamil Eelam (LTTE). In Colombo, the government said government troops have confined Tamil rebels to a narrow strip of 4.5 square kilometers in north-eastern Sri Lanka, where a final battle to rescue civilians trapped in the area is under way. The government estimated that 20,000 civilians remained trapped in the area, but UN agencies said the figure is around 50,000. The government has accused the LTTE of holding the civilians against their will as human shields, while the rebels have accused the military of attacks that have killed scores of civilians. The UN said it and the government of Sri Lanka made Tuesday an urgent appeal for 50 million dollars to meet the most immediate humanitarian needs of the civilians threatened by the fighting in the country's northern parts. An estimated 190,000 people are in government-held camps after thousands of them escaped the fighting areas in recent days.