Image caption The blaze was extinguished within 10 minutes, officials in Corvallis say

A fire at an Islamic centre in the western US state of Oregon was started intentionally, US police say.

They say the blaze gutted one room of the Salman Alfarisi Islamic Center in Corvallis. No-one was injured.

The centre had been attended by Somali-born teenager Mohamed Osman Mohamud, 19, who was held on Friday for plotting to detonate a bomb at a Christmas tree-lighting ceremony in nearby Portland.

The bomb was a fake supplied by agents in a sting operation.

Police warning

"We eliminated other causes of the fire, and we do have evidence that it was arson," Carla Pusateri of Corvallis' Fire Department said on Sunday.

Officials said the fire started shortly after 0200 local time (1000 GMT) and was put out about 10 minutes later.

Local police said they did not know who started the blaze, but they suggested the centre was targeted because Mr Mohamud had occasionally worshipped there.

Image caption Mr Mohamud is a naturalised US citizen

However, they warned they would tolerate no attack in retribution for Mr Mohamud's foiled attempt.

On Friday, Mr Mohamud, who lives in Corvallis, had driven a van to the ceremony in Portland and was arrested at around 1740 local time, about 20 minutes before the tree lighting was to occur.

He was detained after reportedly making a telephone call he thought would set off the bomb in the centre of Portland.

Prosecutors said Mr Mohamud had shouted "Allahu Akbar!" (God is great!) and tried to kick agents as they closed in.

Mr Mohamud allegedly told the FBI agent that he had been thinking of carrying out a jihad, or holy war, against infidels since the age of 15.

He is a naturalised US citizen who had reportedly been in contact with an associate in north-west Pakistan.

Mr Mohamud has been charged with attempting to use a weapon of mass destruction and is due to appear in court on Monday.