Islamist al Shabaab rebels attacked soldiers from Somalia's semi-autonomous Puntland region, leaving at least nine people dead on Saturday, officials said, in the latest sign of a resurgence by the militants in the area.

Al Shabaab promised last week to step up action in the northern Puntland area - a territory which up to now has escaped the worst of Somalia's turmoil - after merging with another militant group there.

The new alliance could mark set-back for international forces from the African Union, Kenya and Ethiopia, who have been making gains against the Al Qaeda-backed movement in other parts of the anarchic Horn of Africa nation.

Al Shabaab, fighting to impose a harsh interpretation of Islamic sharia law, has said it wants to control Puntland and scrap the licenses of Western oil and gas firms drilling in the area.

Al Shabaab told Reuters it attacked a checkpoint manned by soldiers from Puntland's semi-autonomous government on Friday night and fighting carried on into Saturday.

We first attacked their checkpoint near Bosasso last night. Then this morning they attacked us at Baliqadar, 40 km to the east of Bosasso. We also burnt three of their armed vehicles using landmines, the group's military spokesman sheikh Abdiasis Abu Musab, said.

He said the group, which has been fighting a five year war against Somalia's Western-backed government, had killed 32 Puntland soldiers and lost three of its own fighters.

Local officials gave a lower death count. We received nine dead people and six others were wounded. These include five dead bodies of al Shabaab and three other injured ones who are being kept in the hospital by police, Abdiqadir Mohamud, a doctor at Bosasso Hospital, told Reuters.

In January, Canadian oil and gas exploration company Africa Oil Corp. began drilling an exploratory well in Puntland, the first to be sunk in the country since civil war erupted two decades ago.

Africa Oil and its partners in the two Puntland licences, Australia's Red Emperor and Range Resources.

Al Shabaab has been losing ground around the Somali capital, Mogadishu, to African Union troops and territory in parts of southern and central Somalia to Kenyan and Ethiopian forces.

EXPANDING AU FORCE

About 9,000 Ugandan and Burundian troops in the AU's AMISOM force support the shaky Western-backed government and now control much of Mogadishu, after seizing a major al Shabaab base on Friday.

Last week, the U.N. Security Council voted to expand AMISOM to nearly 18,000 soldiers and incorporate Kenyan forces already in Somalia.

African political and military leaders will meet in Addis Ababa, Ethiopia next week to iron out the finer details of how the expanded force will operate, Kenyan army colonel Cyrus Oguna told reporters in Nairobi.

Oguna said Kenya had conducted two air strikes inside Somalia last week near the border, killing several al Shabaab fighters, he added.

He said AMISOM was supposed to keep the peace across Somalia, including Puntland, but it was not clear which troops will be assigned to the area.

After the meeting that is held in Addis Ababa next week, we will be able to know Puntland falls into which sector, he said.

In another incident in Mogadishu, a would-be suicide bomber died on Saturday after his car prematurely exploded at a checkpoint near a base used by Burundian AU peacekeepers, witnesses said.

One man jumped out of the car before it exploded and was now being questioned, Colonel Nur Hayr, a senior police officer in charge of Hodan District, told Reuters.

(Additional reporting by George Obulutsa in Nairobi and Abdi Sheikh and Feisal Omar in Mogadishu; Editing by Andrew Heavens)