"Efforts to bring in more food and medicines have not yet been successful, and it is imperative that these needs be met."
The International Committee of the Red Cross had said a "humanitarian catastrophe" was unfolding in the region where the government says civilians are being held as a human shield by the Tigers.
The UN, the United States and Britain have asked the Tigers to allow civilians to leave the conflict zone while urging the Colombo government to declare a temporary truce.
Both have rejected the calls.
On Saturday, the defence ministry accused the Tigers of a grenade attack that killed a woman and wounded 13 people who were trying to flee the shrinking area still under rebel control.
The Tigers have denied charges that they are attacking civilians and they say the civilians are staying in the area of their own accord.
Claims b