COLOMBO, Sri Lanka – A government health official said 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.

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

Physician V. Shanmugarajah says it is feared that many more are dead in the attack that began late Saturday and lasted until early this morning.

The doctor, who works in the war zone, called the situation “overwhelming.”