NAIROBI (AFP) - Kenyan police on Wednesday (Sept 5) raided the African headquarters of the China Global Television Network, briefly detaining several journalists as part of an ongoing crackdown against illegal immigrants, an employee told AFP.

Cellphone footage of the raid seen by AFP showed armed plainclothes police bundling Chinese staff into vehicles while demanding that reporters of other nationalities produce their passports or accompany them to the police station.

"They had automatic rifles, it was scary," said one foreign reporter at the state-owned television station on condition of anonymity.

Kenyan police chief Joseph Boinnet confirmed the raid on the office in search of illegal immigrants.

"All the foreigners who were arrested at CGTN have been released after their documents were confirmed to be okay," he told Capital FM radio station.

In a statement, the Chinese embassy said it received a call for help from 13 nationals, eight of whom worked for CGTN, while the five others were employed in the same building.

"They stated that they were detained by Kenyan police even though they held legal documents," read the statement.

Several such events happened recently. The Chinese Embassy (is) expressing its concern to the Kenyan side through diplomatic channels.

CGTN, an international English-language television station, broadcasts across the globe, with major news centers in Nairobi and Washington.

Kenya last month began hunting down and arresting those illegally in the country after holding a 60-day exercise in which every foreigner was required to revalidate their permits - a laborious process that can take up to eight hours.

Last week the interior ministry released a hotline number for members of the public to report illegal immigrants.

"It is extremely worrying that citizens are being encouraged to call a hotline to report cases of suspected undocumented migrants. This approach is likely to ignite xenophobia against foreign workers, refugees and asylum seekers," Amnesty International's regional deputy director Seif Magango said in a statement on Saturday.

China and Kenya maintain strong relations, with Beijing funding numerous infrastructure projects in the country.

China financed 90 per cent of a US$3.2-billion (S$4.4 billion) railway linking Nairobi to the coastal city of Mombasa.