Image caption Mr Mohamud is a naturalised US citizen

A teenager has been arrested in the US state of Oregon after allegedly plotting to carry out a car bomb attack at a Christmas tree lighting ceremony.

Somali-born Mohamed Osman Mohamud, 19, was arrested after reportedly making a telephone call he thought would set off the bomb in the centre of Portland.

However, the bomb was a fake supplied by agents in a sting operation.

Mr Mohamud is a naturalised US citizen who had allegedly been in contact with an associate in north-west Pakistan.

He has been charged with attempting to use a weapon of mass destruction.

'Lot of children'

Mr Mohamud, who lives in the town of Corvallis, had driven a van to the ceremony and was arrested at around 1740 local time on Friday (0040 GMT Saturday), about 20 minutes before the tree lighting was to occur.

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

Court documents said the case began in August 2009 with e-mail exchanges between Mr Mohamud and his alleged associate in Pakistan's North-West Frontier Province.

Special FBI agent Arthur Balizan said: "The threat was very real. Our investigation shows that Mohamud was absolutely committed to carrying out an attack on a very grand scale. I want to reassure the people of this community that, at every turn, we denied him the ability to actually carry out the attack."

The Oregonian newspaper quoted Oregon US Attorney Dwight Holton as saying: "This defendant's chilling determination is a stark reminder that there are people - even here in Oregon - who are determined to kill Americans."

He said there was "no reason to believe there is any continuing threat arising from this case".

An undercover agent had posed as an associate of the Pakistan contact and met Mr Mohamud to discuss the plan, the court papers said.

The agent informed Mr Mohamud there would be "a lot of children" at the ceremony but Mr Mohamud allegedly said he was looking for a "huge mass that will be attacked in their own element with their families celebrating the holidays".

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.