Brussels - UN Secretary General Ban Ki-Moon is "most concerned" by the recent upsurge of fighting in Sri Lanka, he told journalists in Brussels on Thursday.

"I am most concerned at the rapidly deteriorating security situation in Sri Lanka," Ban said on the sidelines of a conference dedicated to the piracy crisis in Somalia.

"I would like to take this opportunity to strongly urge all the parties concerned to respect the call of the UN Security Council, made yesterday, in full and without further delay: too many lives are at stake," he said.

In recent weeks, the Sri Lankan army has pushed deep into territory held by Tamil Tiger rebels, trapping thousands of civilians in the conflict zone.

On Wednesday, the security council in a non-binding statement urged the rebels to surrender, and called on the Sri Lankan government to protect civilians and allow international agencies access to victims of the conflict.

"The UN stands ready to do whatever it can to provide emergency humanitarian assistance and to protect the civilian population," Ban said. (dpa)