A Kenyan fighter pilot whose jet crashed in an area controlled by Al-Qaeda-affiliated Shebab fighters in southern Somalia is missing, the army said Friday.

The Shebab said they shot down the warplane on Thursday and "destroyed" the body of the pilot, who was returning from a bombing raid on an extremist base.

A Kenya military plane crashed Thursday in war-torn southern Somalia, the army said, blaming "technical problems", while the Shebab fighters boasted they had shot it down.

Kenyan troops entered southern Somalia three years ago to fight the al-Qaida-affiliated Shebab rebels, later joining an African Union force.

At least 310 people have been killed and over 220,000 fled their homes in attacks in Kenya this year, the United Nations said Thursday, warning of rising conflict.

Cattle rustling and revenge killings between rival communities are common in Kenya's remote and impoverished northern regions, an area awash with automatic weapons.

Somalia's Shebab insurgents said they had assassinated a former lawmaker and his bodyguard and wounded another MP in a drive-by shooting in Mogadishu on Thursday to show the government they remained a threat.

Gunmen in a moving car opened fire as the lawmaker drove through the center of the city, before racing off, witnesses said. MP Mustafa Mayow was wounded in the attack.

The International Criminal Court on Wednesday gave prosecutors a final week either to strengthen or drop crimes against humanity charges against Kenyan President Uhuru Kenyatta, saying a trial could not be postponed any longer.

"The Chamber directed the prosecution to file a notice, within a week, indicating either its withdrawal of the charges... or that the evidentiary basis has improved to a degree which would justify proceeding to trial," The Hague-based tribunal said in a statement.

Kenya's interior minister and police chief were removed from their posts on Tuesday, hours after Somalia's Shebab rebels carried out a fresh massacre in the northeast of the country.

In a televised address to the nation, President Uhuru Kenyatta also vowed his security forces will "intensify the war on terrorism" after a spate of killings in the country by the al-Qaida-affiliated insurgents.

Somalia's Shebab rebels on Tuesday said they carried out the massacre of 36 quarry workers in northeast Kenya, and vowed to be "uncompromising, relentless and ruthless" in fighting Kenya.

"In another successful operation carried out by the Mujahideen, nearly 40 Kenyan crusaders met their demise after a unit from the Saleh Nabhan brigade raided them in the midnight hours of Monday at Koromei, on the outskirts of Mandera," Shebab spokesman Sheikh Ali Mohamud Rage said in a statement to Agence France Presse.

Gunmen hurled grenades and sprayed bullets at a bar in the northeastern Kenyan town of Wajir late Monday, the latest in a series of attacks in the region, the Red Cross said.

One person was "feared dead" and five others were rushed to hospital with wounds, said the Kenyan Red Cross, which reported "three blasts and gunshots" at a club in the town, where Somalia's al-Qaida-affiliated Shebab and other militia have carried out a string of raids.

A Kenyan policeman was shot dead and another seriously wounded in a new attack by suspected Shebab militants in northeastern Kenya on Saturday, police said.

The shooting, which occurred near the Dadaab refugee camp, came a week after the al-Qaida-affiliated Somali rebels executed 28 civilians in the far northeast.

Authorities in Kenya's troubled port city of Mombasa said Thursday they were allowing four mosques to reopen following a string of raids to hunt for weapons and supporters of Somalia's Shebab militants.

Last week police said they found grenades, ammunition and petrol bombs and detained scores of people in swoops on the Masjid Musa, Sakina, Swafaa and Minaa mosques. One person was also shot dead as they tried to throw a grenade at police.