The UN has issued a fresh appeal for a humanitarian pause or lull in the fighting in Sri Lanka to avoid a "bloodbath" on the beaches.
It says such a development in the north-eastern region "seems an increasingly real possibility".
The latest appeal comes as aid agencies are expressing increasing concern over the safety of more than 100,000 people caught up in the fighting.
The rebels are now confined to a small coastal area in Mullaitivu district.
‘Maximum restraint’
The government has repeatedly rejected international calls for a ceasefire saying this would only allow the rebels to regroup.
The military says it has now captured all rebel-held territory in the north-east after days of intense fighting and has now pushed them into a government-designated "safe zone" set up to protect civilians.
The zone is estimated to be about 20 sq km (12.4 miles) of the coastal area.
Although the government says that its forces are in no hurry to storm the zone in pursuit of the rebels, there are fears that any such attempt would cause a high number of civilian casualties.
"I think if the army goes into the area then we are concerned about the number of casualties there would be," UN resident co-ordinator for Sri Lanka, Neil Bhune, told the BBC
In other circumstances, when you have so many civilians and so many soldiers together it’s a dangerous situation. So, we are calling for a maximum restraint at the moment."
The UN official also called on the rebels to do all they can to ensure people who want to leave the safe zone are able to do so.
But the rebels deny accusations that they are holding civilians against their will.
A senior health official in the conflict zone, Dr T Varatharaja, told the BBC that more than 30 civilians had been killed in the last 24 hours when shells landed inside the designated no-fire zone.
Nearly 65,000 people have already escaped the fighting and they have been housed in relief centres and camps set up by the government in the northern region.
Mr Buhne visited these camps a few days ago. He said conditions in them were still not satisfactory despite the government’s efforts to improve them.
Responding to allegations that the camps are little better than concentration camps, Mr Buhne said that a "sincere effort is being made to house the people and provide food to them… I think some of the more dire descriptions of the facilities are exaggerated".
Earlier the UN under-secretary general for humanitarian affairs and emergency relief, John Holmes, warned of a "bloodbath" on the beaches of northern Sri Lanka in an article published in the British daily The Guardian.
"I fear the combatants may be gearing up for a final confrontation. This is a grave situation."
Sri Lankan military spokesman Brigadier Udaya Nanayakkara has denied that the army was responsible for civilian deaths.
"First of all we don’t engage the safe zone and there is no requirement for us to fire shells at the moment," Brigadier Nanayakkara told the BBC.
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