KAMPALA: Ugandan police pinned their hopes on an unexploded suicide vest Wednesday to help them track down suspects in the double bombings that killed at least 76 people watching the World Cup final.

The blasts that ripped through a crowded bar and a restaurant in Kampala on Sunday have been claimed by Al-Qaeda-inspired Shebab insurgents in Somalia, who called them retaliation for the presence of Ugandan troops in Mogadishu.

Police chief Kale Kayihura said a suicide vest -- laden with explosives and fitted with a detonator -- had been found packed in a black laptop bag at a club in Kampala`s Makindye district on Monday.

"We have established that what was found at the discotheque was in fact a suicide vest, and it could also be used as an IED (improvised explosive device)," he told reporters.

Several arrests have been carried out, but Kayihura did not specify how many, nor did he give their identities.

While the bombers` modus operandi appeared to support the Shebab`s claim of responsibility, the police chief pointed a finger at a homegrown Muslim rebel group known as the Allied Democratic Forces (ADF).

"Shebab is linked with ADF," he said. "ADF is composed of Ugandans, Shebab and ADF are linked to Al-Qaeda."

But Ismael Rukwago, a senior ADF commander based in Democratic Republic of Congo, denied any involvement.

"We are not part of this thing, we are absolutely denying. We have no reason, these are innocent people," he told AFP by telephone, adding that his group has repeatedly called for peace negotiations with Kampala.

President Barack Obama said Tuesday that groups such as Shebab and Al-Qaeda saw Africa as a place where life was cheap.

In an interview with the South African Broadcasting Corporation (SABC) to be broadcast early Wednesday, the US leader took aim at the motivations of extremists on the continent.

"They see it (Africa) as a potential place where you can carry out ideological battles that kill innocents without regard to long-term consequences for their short-term tactical gains," he said.

A senior US official earlier said there was reason to believe Shebab`s claims of responsibility and expressed fears the group may plot strikes outside of Africa.

The official, speaking on condition of anonymity, said that although the United States had tracked the rebel group, also called Al-Shebab, and knew about its Al-Qaeda links, it had no forewarning of the strikes in Kampala.

"Al-Shebab has a domestic agenda inside of Somalia that is a bloody one. It also has a terrorist agenda that now has manifested itself outside of Somalia," the official told reporters in a conference call.

The official said it was known that a number of Americans had gone to Somalia to link up with the group, which has threatened US interests, but said law enforcement agencies in Washington were aware of the potential threat.

If confirmed as the work of Shebab, the Uganda attacks would be the group`s first strikes outside Somalia, marking an unprecedented internationalisation of Somalia`s 20-year-old civil conflict.

"We are behind the attack because we are at war with them," Ali Mohamoud Rage, the Shebab group`s spokesman, told reporters in Mogadishu on Monday.

The movement`s top leader had warned in an audio message earlier this month that Uganda and Burundi would face retaliation for contributing to an African Union (AU) force supporting the Western-backed Somali transitional government.

The Shebab accuse the AU force (AMISOM) of killing civilians during its operations around the tiny area of Mogadishu housing President Sharif Sheikh Ahmed`s embattled administration.

"We will continue the attacks if they continue to kill our people," Rage said. "This was a defensive measure against the Ugandans who came to our country and killed our people. This was retaliation for their actions."

The Ugandans were the first to deploy to Somalia in early 2007.

Burundi, which also has troops in Somalia, said it had stepped up security in response to the Shebab`s threat.

Kenya, which shares a long and porous border with Somalia, also said it would thwart any attacks by the Islamists who have in the past warned they would attack Nairobi.

The bombings were the deadliest in East Africa since Al-Qaeda attacks against the US embassies in Kenya and Tanzania in 1998.

BDST:0930 HRS, July 14, 2010