The United Nations sent its top humanitarian official to Sri Lanka Saturday to secure the safety of up to 50,000 civilians trapped in fighting between government forces and Tamil Tiger rebels. The dispatch of Under-Secretary General for Humanitarian Affairs John Holmes on a three-day mission coincided with a White House call for an immediate ceasefire and a strong statement of concern from the Group of Eight (G8) industrialized nations. “The top priority remains the preservation of the lives of the tens of thousands of civilians still trapped inside the combat zone,” Holmes said in a statement released ahead of his arrival here. The United Nations believes up to 50,000 non-combatants are still trapped in the tiny sliver of jungle where the Sri Lankan military has surrounded the remnants of the once powerful Liberation Tigers of Tamil Eelam (LTTE) army. Around 100,000 civilians have already managed to escape the area, and Holmes said he also wanted to inspect the government-run camps where critics say the refugees are being held in prison-like conditions. The UN says dozens of its local Tamil employees are also detained in the camps and wants them freed together with their families. The plight and suffering of those caught in the fighting prompted US President Barack Obama's administration on Friday to urge an end to hostilities. “We call on both sides to stop fighting immediately and allow civilians to safely leave the combat zone,” the White House said in a statement. The Sri Lankan government has so far resisted all calls to halt an offensive that is now on the brink of wiping out the LTTE who have been fighting for an independent Tamil homeland since 1972. The LTTE issued their own call for foreign intervention, warning that the civilians under their control were facing “imminent” starvation. GoC 58 Division Brig Shavendra Silva said security forces missed “by a whisker” a rare chance to capture Tamil Tigers supremo Velupillai Prabhakaran and his top aides recently. “We got to know that Prabhakaran had moved through the Pudukudiryirippu-Iranmalai road on a day between March 29-31, just about two days before the army fully laid seige to that area,” Silva said. “Yes I regret we missed him by a whisker or else things could have been over faster,” he said, adding Prabhakaran cannot escape through the road. He claimed that the rebel leader had limited options – to give up, get killed or commit suicide.