The TRO, which is outlawed in several countries, including the US, said the UN had levelled its criticisms against the Tigers to hide "their own failures".
'Exhaustion and despair'
James Elder, a spokesman for Unicef, told Al Jazeera that some local staff had asked to leave the war zone amid the intense fighting between the LTTE and Sri Lanka's military.
He said: "There are two critical things here - one, that women and children be allowed to leave the conflict zone and go to safe areas where they can be reached with support.
"The other one is that both sides to this fight ... need to ensure absolute protection for those [trapped] civilians and that has not been happening."
The International Committee of the Red Cross (ICRC) said that families were arriving at a designated "safe zone" inside rebel territory "in a state of utter exhaustion and despair, hoping to be treated and rescued".
"But the reality is that there is an almost complete lack of medicine and relief items there," said Paul Castella, the head of the ICRC in Sri Lanka.
"We did save lives today, but many people remain behind, helpless and anxiously waiting to be evacuated. It is now a matter of life and death."
'Verge of defeat'
Unicef has long-accused the Tigers, who are fighting for an independent state in Sri Lanka for ethnic Tamils, of recruiting child soldiers.
|The Tiger have always denied that their fighters kill civilians or use 'human shields' [AFP]
The organisation has said that more than 6,000 children have been recruited since 2002.
The Sri Lankan government has in turn been accused by Tamil politicians of ignoring the safety of civilians in its campaign to wipe out the LTTE.
Rajavarothayam Sambanthan, from the Tamil National Alliance, said that more than 2,000 civilians have been killed since December and more than 4,500 wounded.
Brigadier Udaya Nanayakkara, a Sri Lanka military spokesman, denied the allegation, saying that the military had slowed down its campaign out of concern for civilians.
Government forces say they are on the verge of defeating the LTTE after more than 25 years of civil war.
Estimates on the number of civilians trapped in the conflict zone range between 70,000 and 200,000.
The UN, the United States and Britain have asked the Tigers to allow civilians to leave the conflict zone while urging the government in Colombo to declare a temporary truce.
Both have rejected the calls.