International powers pledged yesterday to boost aid for Somalia to tackle Islamist militancy, piracy and political instability, warning that failure to help now could hurt the rest of the world.

In a final communique, 55 countries and organisations gathered in London said they would act to punish anyone trying to prevent a peace process under which the fragile transitional government will hand over power in August.

But even as the leaders discussed the Horn of Africa nation’s attempts to end two decades of chaos, Somalia’s Al-Qaeda-allied Shebab insurgents vowed to “wage war” against any international peace initiative.

British Prime Minister David Cameron said the problems Somalia faced, ranging from Shebab militants and pirates plaguing the Indian Ocean, had global implications.

“Supporting these efforts is not just right for the people of Somalia, it is right for the whole world. Because when pirates are disrupting vital trade routes and kidnapping tourists and when radicalism is poisoning young minds and breeding terrorism, it is in all our interests to support the Somali people in taking back their country,” he said.

UN chief Ban Ki-moon and US Secretary of State Hillary Clinton were among those attending the talks in London, along with Somalia’s President and Prime Minister, the Arab League and the African Union.