A British journalist working for The Times of London newspaper was detained by Kenyan security at Nairobi airport on Friday and was held without explanation or charge.
Jerome Starkey, 35, was locked in a cell overnight after arriving in Kenya from the UK late on Thursday.
"Just been arrested at the airport on orders of security services," Starkey tweeted early on Friday morning, posting a photograph of an untidy room with metal bunk beds inside the airport terminal.
Officers told Starkey a "security block" had been placed on his passport but were unable to provide any further information.
An award-winning journalist, Starkey has lived in Kenya since 2012 when he was appointed Africa correspondent for The Times after years working in Afghanistan.
Starkey has reported extensively on terrorism, security, miscarriages of justice, conservation and drugs trafficking while based in East Africa.
He had been questioned by immigration, detectives and anti-terrorism police but after more than 15 hours in custody had still not been charged by Friday afternoon.
A spokesman for the British High Commission in Nairobi said: "We are in contact with local authorities and are providing assistance to a British man following his detention in Nairobi."
Starkey on Friday said immigration officials at the airport had denied him access to a lawyer.
"A lawyer who came to see me was just denied access to the airport by officials who said immigration hadn't detained anyone #WhyIloveKenya," he posted on his Twitter page.
The journalist also took issue with an Anti-Terrorism Police Unit officer's move to take photos of him.
"Still in custody at JKIA. Just been papped by an officer from the (British trained) anti-terror unit ATPU. Impeccably polite," he said.
Additional reporting by Harry Misiko.