Ban Ki-moon, the United Nations' secretary-general, has made a surprise visit to the Somali capital Mogadishu, the first by a top UN official since the start of the conflict in 1991.

Wearing a bullet-proof vest, Ban was welcomed by Abdiweli Mohamed Ali, the Somali prime minister, at the city's airport on Friday before making his way to the presidential palace.

Al Jazeera's Peter Greste, reporting from Mogadishu, said the visit "was intended to underline just how much ground the UN-backed Transitional Federal Government [TFG] has made over the past year with the help of African Union peace keeping mission here".

Following his arrival, Ban announced that the UN's political office for Somalia would be relocated from Kenya to Mogadishu.

"It is a very important statement of confidence in the capacity of TFG to try to maintain some degree of stability and security here," Al Jazeera's Greste said.

Security 'not guaranteed'

Ban's brief visit came after the TFG and supporting forces from the African Union (AU) regained some territory from the Shabab armed group, which is seeking to take control of Somalia and institute Islamic law. Though Shabab has been pushed back, it still controls large swaths of the country.

One year ago, Shabab even controlled sections of Mogadishu itself, and Greste said the TFG's hold of the capital remains "tenuous at best".

Kenya also recently launched a limited offensive into Shabab-controlled territory in southern Somalia.

"[The TFG] doesn't even control the capital particularly well, I have to say. Security in this city is, by all means, not guaranteed," our correspondent said.

Mogadishu fell into chaos in 1991 after its last president was ousted. Warlords then turned on each other, plunging the country into a near perpetual state of anarchy in the past two decades.

After the failed US military intervention in 1993, the international community largely pulled out of Mogadishu.

The city hosts few foreign embassies, and most Western aid workers have withdrawn due to increased security risks. The UN's mission for Somalia has been based in Nairobi for several years.