The UN Security Council is to vote to increase the African Union peacekeeping force in Somalia by more than 5,000 soldiers, diplomats have said.

The resolution will increase the number of troops in the country to 17,731 from its current level of 12,000.

The vote on Wednesday comes ahead of an international conference on Somalia to be held in London.

British Prime Minister David Cameron told the BBC the threat from Somalia's al-Shabab militants was "substantial".

"It is based on the fact that al-Shabab is an organisation that has now explicitly（明确地） linked itself to al-Qaeda, and it encourages violent jihad（讨伐异教徒） not just in Somalia but also outside Somalia," Mr Cameron said.

The armed Islamist group controls many southern and central parts of Somalia, which has been without an effective central government since 1991.

Political solution

Nearly 1.5 million Somalis have been forced from their homes during the conflict.

Last year, al-Shabab was forced out of many parts of the capital, Mogadishu, by forces allied to the UN-backed government. Since then, the group has also lost ground in other areas.

In October, Kenyan troops crossed over the border in pursuit of al-Shabab members it blames for a series of kidnappings in Kenyan territory.

Earlier this month, they captured the key town of Badhadhe, some 180km (110 miles) south of the port of Kismayo.

Ethiopian troops have also entered Somali territory to move against the Islamist militants.

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