Ten al Shabaab rebels were killed in a Kenyan air raid on the southern Somali town of Jilib on Sunday, the military said, as the east African nation fights to rid Somalia of the al Qaeda-linked militants.

Kenya moved its troops into Somalia in mid-October in pursuit of Somali insurgents it blames for a series of kidnappings on Kenyan soil and frequent assaults on its security forces in the border province of North Eastern.

Residents and officials told Reuters earlier on Sunday that at least 12 civilians were killed when two Kenyan jets bombed Jilib.

Intelligence reached us that they were there and we carried out an opportunistic strike. We killed 10 al Shabaab fighters and there was no collateral damage, Emmanuel Chirchir, the Kenyan military spokesman, told Reuters on the phone.

Chirchir said al Shabaab was spreading propaganda by claiming that civilians and children had been killed in the raid. He said a senior official of the group was killed in an earlier strike on the port of Kismayu, a few days ago.

The jets bombarded two places, an al Shabaab base and a nearby IDP camp, Hassan Abdiwahab, a resident in Jilib, 120 km (74 miles) north of the port of Kismayu, told Reuters.

An al Shabaab leader in the town said the five bombs dropped by the planes hit a bus stop, the IDP camp and an area just outside of the town.

A top official of the group, Sheikh Muktar Robow Abu Mansoor, on Thursday urged al Shabaab followers to attack Kenya with huge blasts in retaliation for the campaign that is being carried out jointly with Somali government troops.

The call followed two grenade attacks in the capital Nairobi that killed one person and injured at least 20 on Monday. Unidentified militants also carried out two attacks on vehicles in the remote northern Kenya.

Mohammud Farah, spokesman for the Ras Kamboni militia that is allied to the Somali Transitional Federal Government, said they seized a four-by-four vehicle laden with explosives that was headed to Kenya.

Our forces in patrol found the car 8 km away from the town on its way to Kenya and we have discovered different types of explosive materials in the car, Farah told Reuters from Dhobley town, which is close to the border.

The vehicle was carrying 10 passengers, four of whom were identified as al Shabaab fighters, he added.

Kenya said on Saturday it was committed to withdrawal from Somalia once it is satisfied that it has stripped the al Qaeda-linked group's capacity to carry out attacks across the border.

Although the Kenyan chief of defence forces said his troops had chased al Shabaab from the whole of Gedo region, the two-week old campaign has been slowed considerably by heavy rains.

Chirchir said the intense rains had started to abate, allowing Kenyan forces to plan an offensive of Afmadow in Lower Juba region, where al Shabaab has been digging in after reinforcing with fighters from other areas.

Now that the rains have subsided, the taking of Afmadow is likely. It should be very soon, he said.

Two Ugandan soldiers were injured on Saturday when African Union troops came under an al Shabaab attack in Mogadishu.

Rwanda's President Paul Kagame, South Africa's President Jacob Zuma and Tanzania's President Jakaya Kikwete expressed their support for Kenya's military action in Somalia, the Kenyan presidency said in a statement from Perth, Australia, where President Mwai Kibaki was attending the Commonwealth summit.

(Additional reporting and Writing by Duncan Miriri in Nairobi; Editing by Karolina Tagaris)