A suicide bomber blew himself up Tuesday in central Mogadishu after being arrested, killing two soldiers and wounding at least four civilians, a security official said.

"A man was detained by soldiers driving a car we believed was full of explosives, but when the soldiers told the driver to open the car, he detonated explosives on his body," said government security official Abdi Hashi.

A policeman was killed and three people wounded in an explosion in Dadaab refugee camp Monday, the latest in a spate of grenade and landmine attacks in Kenya's border regions with Somalia.

"One person has been killed in the explosion, three injured," said Kenya Red Cross spokesperson Nelly Muluka, adding that the blast was in the Ifo II section of Dadaab, the world’s largest refugee camp complex.

A suicide bomber blew himself up at a military base in Mogadishu Wednesday, killing four people but failing to enter the compound, officials and witnesses said.

"The suicide bomber tried to enter the compound but guards stopped him, when he then detonated his bomb, killing three people on the spot including himself," said Farah Barre, a government security official.

Somalia's Islamist Shebab rebels ordered 16 international aid agencies shut Monday in areas they control after armed raids on several offices, and warned more would follow if they did not toe the line.

"Any organization found to be supporting or actively engaged in activities deemed detrimental to the attainment of an Islamic State, or performing duties other than that which it formally proclaims, will be banned immediately without prior warning," the Shebab said in a statement.

A Kenyan soldier was killed and four seriously wounded Thursday when an explosive device blew up their truck close to the border with war-torn Somalia, an army spokesman said.

"Five KDF (Kenya Defense Force) soldiers were seriously injured and have been airlifted to Garissa for treatment," Major Emmanuel Chirchir said, adding that one later "succumbed to his injuries."

Several hundred Ethiopian troops crossed on Saturday into southern and central Somalia, local elders said, but Addis Ababa dismissed the reports as "absolutely not true."

"There are several hundred Ethiopian troops here in lorries and some armored vehicles too," said elder Abdi Ibrahim Warsame, speaking by telephone from Gurel town, in Somalia's central Galgudud region.

At least three explosions rocked Islamist rebel-held regions outside Somalia's capital, witnesses said Monday, with some reporting it to be an aerial attack.

A huge blast was reported in the Shebab-held Afgoye region late Sunday, some 30 kilometers south of Mogadishu.

A blast went off Saturday along a road in the world's largest refugee camp in eastern Kenya near the border with Somalia, but no one was injured, officials said.

The explosion appeared to be minor and one of the officials said if it turns out to be an explosive device planted by insurgents it may have been improperly wired. The two officials spoke on condition they weren't identified.

Kenya said Wednesday that Somali Islamist rebels had received a third planeload of armaments, as its forces prepare to push forward against the Al-Qaida-linked militants in the war-torn nation.

Kenyan soldiers and tanks pushed into Shebab-controlled southern Somalia some two weeks ago to fight the insurgents and curtail their ability to launch cross-border attacks.

A Kenyan air raid at the weekend that struck a camp hosting thousands of displaced Somalis has killed five people, after two victims succumbed to their injuries, an aid official said Monday.

A bomb on Sunday hit the camp, in the southern town of Jilib, where some 9,000 internally displaced children have sought refuge.