The truck accidentally blew up outside a police station near the eastern city of Batticaloa [Reuters/adaderana.lk]

At least 20 people have been killed and dozens of others injured after lorries carrying explosives blew up accidentally in Sri Lanka, officials have said.

The lorries were parked next to the police station in Karadiyanaru, near the eastern port of Batticaloa.

One of them exploded, setting off two others, Major General Ubaya Medawala, a military spokesman, told Al Jazeera.

The explosives were meant for road construction being carried out by a Chinese firm.

"The explosives were kept for safety at the Karadiyanaru police station," he said.

Medawala said it was unclear what triggered the blast but confirmed that officials believed it had been an accident.

"Sabotage is completely ruled out," he said.

Most of the victims were police officers, who were handing out the explosives to contractors for blasting rock on a nearby project. Two Chinese nationals were among those killed. 

The force of the blast obliterated the building and surrounding area, which was littered with rubble, twisted vehicles and bodies. Only the large external walls of the station were left standing, although they were also damaged.

Shanthi Udayakumar, a nurse at the nearby Batticaloa hospital, about 15km from Karadiyanaru, was on duty at the time of the explosion.

"I could feel the tremors of the blast," she said. "Lots of injured people are being brought in."

A police spokesman said the contractors were working for state-run China Overseas Holdings Limited, a construction company carrying out building work in the area which was ravaged by the government's decades-long war against Tamil Tiger rebels.

Karadiyanaru is a fishing village that was previously under control of the Liberation Tigers of Tamil Eelam.

The civil war ended in May last year when government troops crushed the rebels in a military offensive that has since been dogged by war crimes allegations.

Source: Al Jazeera and agencies