The blaze erupted as the West Atlas' sister rig, the West Triton, which is about two kilometres from the platform, managed to intercept the blown-out H1 wellbore at the PTTEP-operated development on its fourth attempt.

The H1 well blew out on 21 August.

As work got under way this morning to kill the well with heavy mud, the installation caught fire.

PTTEP said the fire is burning around the cantilever portion of the West Atlas, which lies directly above the wellhead platform.

The company evacuated 113 non-essential personnel from the West Triton, adding that the crew on two nearby work vessels are safe.

No one has been working on the West Atlas since the blowout.

A PTTEP spokesman confirmed that the platform and rig are still ablaze, and that non-essential personnel had been evacuated from the West Triton and flown to the Australian mainland about 200 kilometres away.

He declined to comment when asked whether the evacuation was prompted by fears the fire could ignite hydrocarbons on the sea surface surrounding the stricken platform.

He later said: "No evidence currently suggests the fire would spread to the sea."

He said the cause of the blaze was not yet known, and declined to comment on whether work on the relief well may have played a role in the fire.

At a doorstep press conference held in Perth this afternoon, PTTEP chief financial officer Jose Martins said the fire was being fuelled by oil and gas and the only way to stop it was to plug the leak.

"The measures which we have been able to take so far can only mitigate the fire, they will not stop the fire," the Australian Associated Press quoted him as saying.

"The best way to stop the fire is to complete the well-kill and stop the flow of oil and gas at the surface of the H1 well, cutting off the fuel source for the fire."

Earlier, Australia's federal Resources Minister Martin Ferguson said in a statement: “The government remains deeply concerned about this incident.”

He added: "Current operations are focused on reducing the intensity of the fire.

"Some of the world's leading experts are working to fix the leaking well and respond to this latest problem."

Ferguson said the National Offshore Petroleum Safety Authority had been called out to help fight the fire, while Geoscience Australia and the Australian Maritime Safety Authority are providing technical advice.

A specialist fire fighting team from Alert Well Control has been flown to the site and is assessing the blaze.

PTTEP said a fire fighting vessel, the Nor Captain, had earlier doused the fire with water before moving away. The vessel is currently on standby about two nautical miles away from the West Atlas rig.

Sea water has been pumped into the relief well from the West Triton in a bid to “wet” the gas and help bring the fire under control. It is understood pumping operations are ongoing.

The blowout has cost PTTEP an estimated A$177 million (US$162 million), with clean-up costs alone totalling around A$5 million.

"This spill has been a disaster from the outset," Australian Greens Senator Rachel Siewert told the Australian Broadcasting Corporation this morning.

"Coupled with the environmental impacts of the oil entering the ocean, the potentially hazardous effects of the dispersants being used and the threat to fisheries both here and in Indonesia, now we have a fire on our hands."'

An estimated 500,000 litres of oil and condensate has spewed into the Timor Sea since the blowout.

PTTEP said 300 to 400 barrels of oil per day was leaking from the damaged wellbore, but the Department of Resources, Energy & Tourism told a Senate committee it believed up to 2000 bpd is being leaked into the sea.

The area surrounding the Montara development is home to a wide variety of marine wildlife, including several species of dolphin, sea turtles, sea snakes and humpback whales, as well as migratory sea birds.

On Friday, the federal government released a report saying birds and marine species were at risk from the spill.

The report said that while the total effects of the spill were yet to be determined, scientists had found dead and dying birds as well as sea snakes in the spill zone.

Over five days of observation, 462 whales and dolphins, 2801 birds, 62 sea snakes and 25 turtles were logged in the affected area.

A WWF-Australia spokesperson was not immediately available for comment.

However, last week the group issued a report claiming the spill would have a disastrous effect on the marine environment.

Published: 01 November 2009 13:38 GMT  | Last updated: 02 November 2009 01:16 GMT