NAIROBI, Kenya (AP) — A police report says extremist gunmen ambushed an ambulance carrying a pregnant woman and killed her husband before setting the vehicle ablaze in northern Kenya, as such attacks are again on the rise.

The report seen by The Associated Press said the attack took place just before midnight Tuesday in Mandera county. Previous attacks in the region have mainly targeted non-Muslims. Other passengers in the ambulance were injured slightly, the report said.

The al-Qaida-linked al-Shabab extremist group in neighboring Somalia has vowed retribution on Kenya for deploying troops since 2011 to fight it.

Since December 2019, al-Shabab has increased the frequency of its attacks in five Kenyan counties along the Somali border: Lamu, Garissa, Wajir, Tana River and Mandera.

The frequency of attacks slowed in April, May and June as the coronavirus spread, but since July, Kenya’s security forces have seen an increase in their vehicles being hit by roadside bombs.

The frequency of attacks has increased this month in the five Kenyan border counties. A government intelligence report seen by the AP said 40 al-Shabab extremists crossed into Kenya to carry out various attacks, including the abduction and beheading of a chief in Wajir county.

Kenya special forces retaliated on Sunday, raiding an al-Shabab camp in Lamu county and killing seven suspected militants.