A remote-controlled bomb in Somalia has killed two aid workers, their driver and a local journalist in the southern town of Kismayo. Nick Wadhams has the story from Nairobi.

A spokeswoman for the aid group Doctors Without Borders, Susan Sandars, would only say that an incident had occurred, but refused to give any more information.

"At the moment, all I can say is that we can confirm that a security incident has taken place in Kismayo where MSF has a team working. We are still investigating the details of that, but when I get more information I can certainly give it to you. But at the moment we are unable to confirm anything else," she said.

The identities of the aid workers and driver were unknown.

Later in the day, the National Union of Somali Journalists identified the slain reporter as Hassan Kafi Hared, 36. Police officials in Kismayo say the journalist died after being brought to a hospital while the other three were killed instantly in the blast.

As a result of the explosion, the few international aid groups working in the region have been advised to suspend all activity, cancel any planned trips there and make sure their movements and communications are not being tracked.

The Associated Press quoted a worker at the Kismayo hospital as saying that the aid workers had been working there for four months.

The Somali Journalists Union said that Hared, the father of three children, was working for the government-run Somali National News Agency at the time he was killed. It demanded that Somalia's Transitional Federal Government bring the attackers to justice.

The transitional government has no control over Kismayo, which is run by a regional clan. Across the country, the government has been unable to maintain control in the year since Ethiopian troops crossed the border and helped it oust the Union of Islamic Courts, which had taken over much of Somalia.

The African Union recently warned that insurgents in Somalia were spreading out as part of a campaign to further weaken the transitional government's forces. It listed the southern province where Kismayo is located as one of the areas where the insurgents were newly active.