LAMU, Kenya, June 13 (Xinhua) -- Four al-Shabab militants were killed after an improvised explosive device (IED) they were setting up apparently detonated prematurely in Kenya's coastal Lamu region early Thursday, the police confirmed.

A number of militants were also injured in the 3 a.m. incident near a bridge in Lamu East, said Lamu security operation director Joseph Kanyiri.

"I can confirm that four of the militants died from an IED explosion," he said. "It seems the device went off before they were done setting it up, killing three militants on the spot while another died a few minutes later.

"Three badly charred bodies were recovered on the scene while another was picked up a few meters away. It seems he was trying to get away but succumbed to injuries," Kanyiri added.

The area falls within the infamous Boni forest where a security operation, dubbed Linda Boni, has been underway since 2015 to flush out militants there.

The militants have been using the forest to stage attacks on local civilians and security personnel.

Kanyiri said three loaded AK-47 magazines, 12 loose rounds of ammunition and a magazine pouch were also recovered at the scene.

The tourism resort region of the coast has been a target of terror attacks in the past, often staged by al-Shabab terrorists who waged a war against Kenya soon after it deployed its military to war-ravaged Somalia in October 2011.

Kenyan police believe al-Shabab remains a major threat in the border areas, noting that the terror group's targets include security personnel and establishments along the border as well as commuter vehicles plying routes along the border and coastal regions.