At least 257 civilians have been killed and 814 wounded in a massive artillery barrage fired by Sri Lankan forces into the northern war zone, a government health official confirmed Sunday.

The military has denied launching the attack, saying it was only using small arms in its effort to wipe out the Tamil Tiger rebel group.

Physician V. Shanmugarajah said it is feared that many more are dead and already buried by relatives in the attack that began late Saturday and lasted until early Sunday.

The doctor who works in the war zone called the situation "overwhelming."