At least six people are dead after a blast in the Somali capital Mogadishu, police have said.
The suspected bomb was in a vehicle parked near a popular hotel on a main thoroughfare running through the city.
Britain's ambassador to Somalia, Neil Wigan, reports that he heard a "major explosion" at Mogadishu International Airport.
Fifteen people have been killed in a suicide bomb and gun attack on an office of the United Nations Development Programme in the Somali capital Mogadishu - the first major assault on the UN by Somali Islamist militants in years.
The country's interior minister told reporters: "So far we have confirmed four UNDP foreign staff who were responsible for security, four Somali guards and seven militants."
A suicide bomber and several gunmen have attacked an office of the United Nations Development Programme (UNDP) in the Somali capital Mogadishu, a senior police officer and a witness said.
"A suicide bomber blew himself up at the gate of the UNDP and then several armed fighters went in and opened fire inside," Abdikadir Mohamed, a senior police official told Reuters.
The UNDP compound is several hundred metres from the city's fortified airport that serves as the main base for an African peacekeeping force battling Islamist militants in the Horn of Africa country.
A loud explosion has been heard near the Somali capital's heavily-fortified international airport followed by bursts of gunfire, a Reuters witness said.
A plume of thick black smoke billowed into the sky above Mogadishu, a city that has been dogged by suicide bomb attacks since al-Qaeda-linked militants were driven out almost two years ago.
Foreign Secretary William Hague said he "strongly condemns" the terrorist attacks that took place in the Somali capital of Mogadishu, killing at least 19 people.
Mr Hague said in a statement, “We extend our deepest sympathy to the victims and their families. Somalia is emerging from decades of conflict. The actions of terrorists only prolong the suffering of the Somali people".
“The UK and the international community, as we saw at last week’s G8 Foreign Ministers’ meeting, remain committed to helping the people of Somalia achieve peace, security and development", he continued.
"Those responsible for terrorist acts should face justice”, Mr Hague added.
At least 19 people have been killed in the Somali capital in a series of bomb attacks carried out by militants linked to al-Qaeda and in subsequent gun battles.
A bomb exploded outside law courts in Mogadishu as gunmen stormed the compound. Security forces then arrived and battled the fighters inside.
Later, a bomb exploded near an African Union and Turkish Red Crescent convoy on the way to the airport.
The attack has been claimed by al Shabaab - a militant group linked to al-Qaeda.
The Somali interior minister has said that all nine attackers have been killed after a militant assault on a court in the capital Mogadishu.
A large blast has been heard in an area near the airport in the Somali capital of Mogadishu, just hours after a series of explosions at law courts in the capital and gunmen stormed the building, residents said.
"We heard a blast ... and then soldiers opened fire. I see only thick smoke rising into the sky. I do not know what caused the blast. The whole area has been immediately besieged by security forces," one resident, Halima Osman, told Reuters.