Eight Kenyan police officers were killed when their vehicle was blown up by an improvised explosive device in a suspected attack by Somalia-based jihadist group Al-Shabaab, police said.

The incident took place on Tuesday in Garissa county in eastern Kenya, a region on the border with Somalia, where Al-Shabaab has been waging a bloody insurgency against the fragile government in Mogadishu for more than 15 years.

“We lost eight police officers in this attack,” North Eastern regional commissioner John Otieno said. “We suspect the work of Al-Shabaab who are now targeting security forces and passenger vehicles.”

Kenya first sent troops into Somalia in 2011 to combat the Al-Qaeda-affiliated Islamist militants and is now a major contributor of troops to an African Union military operation against the group.

But it has suffered a string of retaliatory assaults, including a bloody siege at the Westgate mall in Nairobi in 2013 that cost 67 lives and an attack on Garissa University in 2015 that killed 148 people.

In Somalia itself, Al-Shabaab has continued to wage deadly attacks despite a major offensive launched last August by pro-government forces, backed by the AU force known as ATMIS.

In one of the worst recent attacks, 54 Ugandan peacekeepers were killed when Al-Shabaab fighters stormed an African Union base in Somalia on 26 May , according to Uganda’s President Yoweri Museveni.

And on Saturday, Somali police said six civilians were killed in a six-hour siege by the militants at a beachside hotel in Mogadishu.