Two Save the Children staff have been kidnapped by unknown gunmen in Somalia, the charity says.

The men, seized from the town of Adado near the Ethiopian border, are a British security consultant and a local aid worker.

Locals said the security consultant also has Zimbabwean nationality.

The BBC's Mohamed Mwalimu says the kidnapping came amid fierce fighting involving tanks and heavy artillery around Adado.

Local residents have told our correspondent in the capital, Mogadishu, that a moderate Islamist group allied to the UN-backed government seized the town from a local warlord on Friday morning, in clashes which left at least seven people dead.

One Somalia expert has told the BBC that the group, Ahlu Sunnah Wal Jama, attacked Adado in retaliating for the kidnapping.

But the group says it moved in because of an increase in activity there by the hardline Islamist group al-Shabab, which has links to al-Qaeda.

... The security consultant had gone there to see if it was safe enough for Save the Children to set up a new base to help malnourished and sick children, along with their families.

But on Thursday evening, a group of masked gunmen stormed the building used as a staff residence.

High walls and a heavy steel gate reportedly forced the kidnappers to climb in through a window before they fled with their hostages into an area said to be controlled by al-Shabab.

Save the Children says it is extremely concerned about the welfare of those being held and calls for their unconditional release.