Nairobi - The American author of a controversial book lambasting US presidential hopeful Barack Obama was Tuesday detained by Kenyan immigration authorities as he prepared to launch his book in the East African nation.

Jerome Corsi was picked up by immigration authorities at a Nairobi hotel just before he was due to present "The Obama Nation: Leftist Politics and the Cult of Personality" to the public.

Immigration authorities refused to comment on the exact reason for Corsi's detention and what the next step would be.

However, the Daily Nation, quoting a source in the immigration department, said that Corsi and his spokesman had been driven to Jomo Kenyatta International Airport and would be put on a plane out of the country.

Corsi had said he would "expose details of deep secret ties between... Obama and a section of Kenya Government leaders... and a subsequent plot to be executed in Kenya should Senator Obama win the American presidency" at the press event.

Corsi had also planned to meet the senator's half-brother, George Hussein Obama, who lives in Nairobi's Huruma slum, to give him a cheque for 1,000 dollars.

George Obama's poverty has provided right-wing commentators with ammunition, saying that it undermines Obama's supposed commitment to family values.

Corsi's 2004 book "Unfit for Command" attacking Democratic nominee John Kerry is credited with helping President George W Bush to election victory.

Observers say that the latest book, which also accuses Kenyan Prime Minister Raila Odinga of supporting radical Muslims, aims to do the same job on Obama, whose father was Kenyan and from the same tribe as Odinga.

Kenya has adopted Obama as Kenyan even though he has only visited the country a handful of times.

He was given a rapturous welcome during his last visit to the village where his grandmother still lives and a beer has even been named after him. (dpa)