6:22pm UK, Sunday May 10, 2009

At least 378 civilians have been killed after Sri Lankan forces fired a massive barrage of artillery shells at Tamil Tiger rebels, a government health official has said.

Sri Lankan military are trying to crush the Tamil Tigers

The military denied launching the attack, saying it was only using small arms in its attempt to try to wipe out the militants.

Around 1,100 people are thought to have been injured in the latest assault.

Physician V. Shanmugarajah, who works in the war zone, called the situation “overwhelming” and said it was the bloodiest day he had seen in the government’s offensive.

He said it was feared many more people were dead and already buried by relatives in the attack.

The pro-rebel Tamilnet website said there had been shelling by government forces.

But military spokesman Brigadier Udaya Nanayakkara said: “We have not used heavy weapons in the area where the Tamilnet says civilians had been killed.”

Displaced Tamil civilians in a hospital

Meanwhile, the Sri Lankan army also said it had uncovered a large contraption that may have been intended as an underwater bunker for the leader of the rebels.

The 360-foot (110-metre) long railway carriage-like construction may have been designed to be wheeled into the sea as a hiding place for Velupillai Prabhakaran, the army claimed.

The unit “could be submerged in water and used as a temporary home,” it said in a statement.

It was not immediately possible to verify the reported find.

The government says it is close to defeating the Tamil Tiger rebels, who are holed up on the northeast coast, after 37 years of ethnic conflict.

Prime Minister Ratnasiri Wickremanayake recently told parliament Mr Prabhakaran, 54, was still leading the group in its battle against an overwhelming military offensive.

Mr Prabhakaran has not been seen for more than 18 months, and there is speculation he may have been killed or already fled the island.

The rebels have been fighting for a separate state for minority Tamils, who have suffered decades of marginalisation at the hands of governments controlled by the Sinhalese majority.