MOMBASA, Kenya (Reuters) - Somali al Shabaab militants killed three police officers on Wednesday during a raid on a northeastern Kenyan town that sparked a day-long gunbattle, a senior police official said.

It was the latest in a spate of attacks on Kenyan security services since Nairobi sent troops into Somalia in 2011 to join a African Union force charged with neutralizing militant and other armed groups and bolstering its U.N.-backed government.

Al Shabaab gunmen attacked the police station in the town of Pandanguo in the coastal district of Lamu around 6 a.m. (0300 GMT), forcing villagers to flee, according to residents. The area is near Kenya’s long, porous border with Somalia.

The militants also raided a dispensary for drugs and houses for food items, clothes and other valuables, witnesses said. Smoke could be seen rising from the village later in the day.

By 6 p.m., three policemen had been killed and a gunbattle was continuing, police said.

“The attackers used RPGs (rocket-propelled grenades),” George Kinoti, Kenya’s national police spokesman, said in a text message. “Reinforcements sent to engage the enemy have killed several terrorists.”

In July 2014, more than 60 militants attacked the same village, torched houses and stole drugs at the same dispensary.

Al Shabaab’s military operations spokesman, Sheikh Abdiasis Abu Musab, confirmed Wednesday’s attack to Reuters by phone.

“We burned the police station and captured cars. Now, today, there are sporadic exchanges of gunfire between us and the police in the outskirts of the town but we still control the town,” he said.

The raid follows a series of attacks in Kenya claimed by Somali militants that have killed at least 28 people in the last six weeks. Most have taken place near the Somali border.

The al Qaeda-linked al Shabaab militia is fighting to overthrow Somalia’s weak, U.N.-backed government and impose strict Islamic law in the Horn of Africa state.

They ramped up attacks in neighboring Kenya after Kenyan troops entered Somalia to join the AU peacekeeping force there.

In a separate incident in Somalia, an air strike killed 10 al Shabaab militants near the southern port city of Kismayo, the Mogadishu government said. It was not immediately clear who carried out the air strike.

Somalia’s government does not have aircraft but mentioned “international partners” in its press statement. Ethiopia, Kenya and the United States have all conducted air raids on Somali territory.