World Bulletin / News Desk

A military offensive has driven Somalia's al Shabaab out of major strongholds and deprived it of revenue sources, but its retreat to a southern valley and northern hills still poses a threat, the U.N. envoy to Somalia said.

The African Union's AMISOM peacekeeping force and Somali soldiers have pushed the group, which wants to topple the Western-backed government, into smaller pockets of territory since launching an offensive last year.

But the group has continued to strike Mogadishu and other government-held areas with bomb and gun attacks from bases in the southern Juba Valley and in northern Puntland's Galgala hills, a region outside the African Union's area of operation.

"The AU-U.N. have just done a benchmarking review of AMISOM and the Somali national army, as well, and certainly they have recognised that Puntland is an area of concern," U.N. envoy to Somalia, Nick Kay, told Reuters on Wednesday.

He said expanding AMISOM's region of operations to the semi-autonomous region of Puntland was "under active consideration", without saying when it might be agreed.

The Somali government has said that the Juba Valley, which lies in the far south near the strategic Kismayo port, was the next target for the military offensive, but has not said when.

Puntland, which has been slowly drawing closer to the federal government in Mogadishu, has agreed to integrate 3,000 of its forces into the Somali national army, Kay said.