By Abdi Sheikh and Feisal Omar
MOGADISHU (Reuters) - An Islamist militia group in Somalia's semi-autonomous Puntland region has merged with the al Shabaab rebel group, said the insurgents on Saturday, a union which threatens to destabilize the relatively secure area targeted by oil explorers.
Al Shabaab said it wanted to scrap the licenses of Western oil and gas firms drilling in Puntland. The al Qaeda-backed insurgents used social media site twitter to declare all oil and gas exploration and drilling licenses nullified.
While they do not hold the administrative control in the region needed to enforce their demand, the militants could try to target installations operated by Western oil companies.
The Puntland administration was not immediately available for comment.
The union comes as the insurgents are being weakened, relinquishing ground to African Union troops around the Somali capital, Mogadishu, and losing territory to Kenyan and Ethiopian forces in parts of southern and central Somalia.
Puntland security officials have previously said the Islamist militia camped out in the Golis hills outside the port city of Bosasso is led by Yasin Khalid Osman.
"I ... the leader of Golis ranges Islamists have signed an agreement with al Shabaab leader Sheikh Muktar Abu Zubeir. We are now al Shabaab," a voice identifying itself as Osman said in an audio recording on al Shabaab's website.
"I urge residents to take part in the jihad against the Christian invaders and the Somali infidels that work with them," he said, referring to the foreign troops inside Somalia.
Osman rarely makes statements and it was not immediately possible to verify his voice.
Last month, 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 licenses, Australia's Red Emperor and Range Resources, are targeting prospective resources of over 300 million barrels of recoverable oil.
In a country that has lacked effective central government for two decades, Puntland's relative stability is showcased by foreign powers advocating a loose federal political system in Somalia.
Some donors have focused development funding on the semi-autonomous region as a reward.
However, Puntland's authorities have blamed the militants for the mounting insecurity in the region. While al Shabaab control parts of southern and central Somalia, they still have a much lighter presence further north.
"The jihad will be redoubled in those areas," Sheikh Ali Mohamud Rage, al Shabaab's spokesman, told Reuters.
(Additional reporting by Adbiqani Hassan in Bosasso; Writing by Richard Lough; Editing by Sophie Hares)