NAIROBI (AFP) - Three Kenyan suspected members of an Islamic State in Iraq and Syria (ISIS) affiliate have been arrested for allegedly planning an anthrax attack, Kenyan police said on Tuesday (May 3).

The man and two women arrested on Friday were part of "an East Africa terror group network, that has links to ISIL," another name for ISIS, according to Kenya police chief Joseph Boinnet.

They are accused of "planning large-scale attacks" including "a biological attack in Kenya using anthrax," said Boinnet.

Mohammed Abdi Ali, the alleged leader of the group and a medical student in Wote, southeast of the capital Nairobi, was arrested in Kenya and is being held in custody for 30 days while investigators gather further evidence.

Two suspected accomplices - his wife Nuseiba Mohammed Haji, a medical intern, and another woman, Fatuma Mohammed Hanshi - were arrested in neighbouring Uganda.

Two other suspects, Ahmed Hish and Farah Dagne, also medics, are on the run in Kenya, with police offering US$20,000 (S$27,000) on wanted notices for each man.

"From our initial investigations, it has been established that the terror network linked to Mohammed Abdi Ali has been engaged in the active radicalization, recruitment of university students and other Kenyan youth into terrorism networks," Boinnet said. "The same network has been facilitating Kenyan youths to secretly leave Kenya to join terror groups in Libya and Syria."

Foreign intelligence sources confirmed Ali's links to ISIS but said he was more likely involved in recruitment of East Africans to fight in Libya and Syria than in plotting an attack in Kenya.

IS recruiters are known to seek out medical students.

Kenyan police compared the group's alleged plots, biological and otherwise, to the 2013 Westgate mall attack in Nairobi in which four gunmen from the East African Al-Qaeda affiliate, the Shebab, killed at least 67 people.

While the Shebab has been active in Kenya since 2011, after the Kenyan army was deployed in southern Somalia, there has been little evidence to date of an IS presence in the country.