Sri Lanka's military says it has captured a Tamil Tiger rebel fortification and killed a senior rebel, as it pushes deeper into a Tamil-controlled enclave in the country's north.

The military said Monday it seized the fortified embankment after heavy fighting Sunday.  It said the rebels suffered heavy losses, including senior Tiger leader Thamilendi.

There was no comment from the rebels.

Sri Lanka's government says troops are moving slowly into the rebels' last stronghold, a coastal strip of territory several kilometers long.  Tens of thousands of civilians are thought to be trapped there.

Also Monday, a delegation of British lawmakers began a visit to Sri Lanka to examine the plight of civilians affected by the conflict.  They are expected to tour displacement camps in the north housing tens of thousands of civilians who have fled the fighting.

The delegation includes former British Defense Secretary Des Browne, who was appointed as Britain's special envoy for Sri Lanka earlier this year.  Sri Lanka's government rejected the appointment as foreign interference.  

In other news, a group of leading human rights advocates condemned the U.N. Security Council's inaction as tens of thousands of civilians remain trapped in Sri Lanka's war zone.  The group said the Security Council no longer can deny the facts on the ground as civilians are held hostage, shelled by government forces and living in abysmal conditions.

It said that some Council members continue to block any meaningful action, despite numerous pleas by diplomats and U.N. officials for the U.N. to call upon the Colombo government and the rebels to stop hostilities.
 
Tamil rebels have been fighting for an independent homeland in Sri Lanka since 1983.  Tens of thousands of people have died in the civil war.

Some information for this report was provided by AP.