The United Nation's Emergency Relief Co-ordinator has ended his visit to Somalia early, following renewed security concerns in the African country.

|PIC1|The UN worker, John Holmes' arrival in Mogadishu coincided with a number of explosions which killed four people, one of which was close to the UN compound in the city

Holmes is the most-senior UN worker to visit the city in a decade and has urged the nation's government to allow humanitarian aid to be transported to its people.

The UN humanitarian agency released a statement saying: "Mr Holmes returned to Nairobi today (Saturday) and plans for a second day in Somalia were cancelled."

In recent developments, gunmen have taken two foreign aid workers hostage in northern Somalia. They have now threatened to kill them if regional authorities try to rescue them, a local official said yesterday.

Abdirahman Mohamed, information minister for the semi-autonomous Puntland region said clan leaders were being sent to negotiate the release of the Kenyan and Briton working for the relief agency Care International, who were seized last Wednesday.

"We don't know exactly what they are demanding but sources close to them say they accuse aid agencies of bias," Mohamed said. "They say Care is helping other areas and ignoring them. I think that is why they abducted the two."

Care International's regional spokeswoman was not immediately available for comment.

Meanwhile, Holmes said that the Somali government had to accept responsibility for its people: "It is their responsibility to look after civilians, to protect civilians and at the very least not to obstruct aid."

The UN coordinator added that the African Union could not boost its peacekeeping forces in the capital until the government had increased security.

Up to 1,600 people were killed in six weeks of clashes between Ethiopian government-backed troops and Islamist and clan fighters before the Ethiopian government declared it had gained victory over the insurgents.

An estimated 20 per cent of Mogadishu's 2 million residents fled the city when violence erupted earlier this year, the BBC has reported.

The chances of peace to the country are always limited, since Somalia has not had a working government since civil war broke out sixteen years ago.