Kenyan police arrest American heading for Somalia

* Man was trying to enter area controlled by insurgents

* Arrested U.S. national told police he is a Muslim

NAIROBI, Oct 12 (Reuters) - An American man has been arrested in northern Kenya while trying to enter an area of Somalia controlled by Islamist insurgents, police and residents said on Monday.

Lawless Somalia is viewed by the international community as a breeding ground for al Qaeda-linked groups which have been carrying out an insurgency against the U.N.-backed administration of President Sheikh Shariff Ahmed.

A witness told Reuters that the man was arrested on Sunday by police manning the immigration office at the border town of Liboi in Kenya's North Eastern province. He was on his way to Qoqani in southern Somalia without any security escort.

"We have arrested the suspect at the border town," said one police officer, who did not want to be named. "The suspect is being transported to the provincial police headquarters for questioning."

Police thought the man's willingness to enter the conflict-torn nation where foreigners are routinely kidnapped for huge ransoms was puzzling, the witness added. The area he wanted to go to is controlled by the al Shabaab rebel group which the United States says is al Qaeda's proxy in Somalia.

The U.S. national had said he was a Muslim and denied any connection to Islamic radicals who make up the bulk of the insurgency in Somalia, said the witness.

Western nations are increasingly concerned about the radicalisation of Somali youth living within their countries. Some have returned to Somalia to boost the insurgents' ranks. (Reporting by Humphrey Malalo and Sahra Abdi; Editing by David Stamp)