The rebels promise more attacks

They blew up a tank at Digboi Oil Refinery and a nearby pipeline but no-one was hurt.

The United Liberation Front of Asom (ULFA) told Reuters news agency that they were behind the pre-dawn blasts and they promised further attacks in coming days.

Firefighters evacuated residential areas around the refinery and had brought the blaze under control by late afternoon.

Officials at the refinery said they heard two loud blasts around midnight (1830 GMT Friday), after which oil started pouring out of a tank and caught fire.

The ULFA's commander-in-chief, Paresh Barua, said the attacks were a "protest" against Indian rule and the group would "continue such targeting in the coming days".

"We're going to target oil installations and security forces," the commander said.

The group is fighting for a separate homeland.

Separatist rebels in the region have often targeted oil installations, bridges and railway tracks.

Five years ago, the ULFA threw grenades into a big crude oil depot, which then burned down.

Digboi Oil Refinery has an annual capacity of 650,000 tonnes and is operated by state-run Indian Oil Corporation.

It is one of the world's oldest operating refineries - set up by British colonial rulers in 1901.