NAIROBI, Kenya – Three women have been killed after they attacked a police station in the Kenyan coastal city of Mombasa on Sunday, a police official said.

One of the women threw a firebomb at officers while another pulled out a knife, Mombasa police chief Parterson Maelo said, adding two policemen were wounded in the attack.

The women, who were dressed in niqabs, were then shot by police. One of the women had a suicide vest that didn’t detonate, another police official said.

No group has claimed responsibility for the attack. But Kenya faces a constant danger of being attacked by adherents of the Somali militant group al-Shabab, which has vowed retribution for Kenya’s deployment of troops to Somalia in 2011.

Maelo said the women arrived at the central police station at about 10:30 a.m. (0730 GMT) to report a stolen telephone.

“While the officers were questioning them about the particulars of the stolen phone one of them drew a knife and another threw a petrol bomb at the officers of the report office,” he said.

Two of the suspects have been identified as Kenyans Fatuma Omar and Tasmin Yakub Abdullahi Farah, police spokesman Charles Owino said. One had a suicide vest that didn’t detonate, he added.

A raid was conducted at Farah’s house, leading to the arrest of three Somali refugees for questioning, he said.

This is the second attack linked to extremism on a police station this year.

In July, a Muslim police officer killed seven colleagues in a standoff at the Kapenguria police station in western Kenya.

Al-Shabab is al-Qaida’s affiliate in the region. It has recruited hundreds of Kenyans and used them in numerous attacks on the country, including the April 2015 attack at Garissa University, which killed more than 148 people.

Recently, al-Shabab attacks in Kenya have been limited to the border towns of Mandera and Liboi near Somalia.

However, Kenya is also struggling to battle the Islamic State group’s recruitment of some of the country’s youths. At least 20 young Kenyans have travelled to Libya to join the extremist group, according to police.

Authorities have also been warning of a plot by extremist medics to unleash an anthrax attack. Four medics are in police custody accused of being IS members and plotting such an attack.

Authorities fear IS is trying to establish a presence in Kenya, East Africa’s biggest economy and telecommunications and transport hub.

There is concern that those who join IS and al-Qaida will be used to launch attacks on Western targets in Kenya and neighbouring countries.

___

A previous version of this story has been corrected to say the women were wearing niqabs, not burqas.