Kenya has denied reports for the UN that many of its citizens are fighting with Somalia's al-Shabab militants.
"This is propaganda," Francis Kimemia, a senior official at the internal security ministry told the BBC.
A report to the UN Security Council said leaders of the al-Qaeda-inspired group regularly travelled to Nairobi to raise funds and recruit fighters.
Al-Shabab controls much of southern Somalia, where it is battling the weak UN-backed government.
Mr Kimemia told the BBC's Network Africa programme that any al-Shabab leaders who passed through Nairobi would be arrested.
He also said the Kenyan authorities were closely watching the country's mosques in case clerics sympathetic to al-Shabab were using them to radicalise young Kenyans and Somali refugees, as alleged by the UN Monitoring Group on Somalia.
Kenya is home to many thousands of Somali refugees, and also has a large ethnic Somali population.
On Tuesday, suspected al-Shabab militants attacked a Kenyan para-military base near the border with Somalia.
BBC
