Ugandan officials have recovered what they've alternately described as an explosives-laden belt or a vest in a trashcan at a nightclub in a suburb of Kampala, the chief of police said Tuesday.
Maj. Gen. Kale Kayihura, the chief of police, said the device - found Monday - was impregnated with ball bearings and was similar to those found at two sites where blasts killed at least 74 people over the weekend.
The device was found along with a detonator and what looked like a laptop bag, Kayihura said.
When a journalist asked him whether this meant there was a third attack planned, he said, "It's possible there was."The police chief said that his office was working with international agencies - but would not specify who. He
also would not say how many people have been arrested in connection with the attack and what their nationalities were.
Earlier, Fred Opolot, executive director of Uganda media center, said authorities had arrested several people but they have not yet been charged in connection with the attacks, Opolot said. "We are trying to find the culprits of this atrocity," he said.
The blasts went off Sunday at two venues - a restaurant and a rugby field - where crowds had gathered to watch the World Cup soccer finals. A Somali Islamist militant movement on Monday claimed responsibility for a trio of bombings.
"And the best of men have promised and they have delivered," said an Arabic statement issued by Al-Shabaab's press office and obtained by CNN. "Blessed and exalted among men - (taking) full responsibility. ...We wage war against the 6,000 collaborators; they have received their response."
The 6,000 is an apparent reference to African Union peacekeepers in Somalia. Uganda contributes troops to the peacekeeping effort. "We are behind the attack because we are at war with them," Al-Shabaab spokesman Ali Mohamoud Rage told reporters at a news conference in Mogadishu, Somalia.
"We had given warning to the Ugandans to refrain from their involvement in our country. We spoke to the leaders and we spoke to the people and they never listened to us," Rage said.
Somalia's Prime Minister Omar Abdirashid Ali-Sharmarke called on the "civilized world to unite in stopping the mindless terror enterprise of Al-Shabab."
"We will work with our partners in Uganda and the international community in bringing the cowards responsible for this heinous act," the prime minister said in a statement released Monday. Meanwhile, al Qaeda congratulated Al-Shabaab in a message posted on pro-jihad web forums.
"Be pleased because all the sincere Muslims are with you joining you in your moments of pleasure and difficulty," read part of the message. The 74 fatalities included 28 Ugandans, one Irish citizen, one Indian, one American and 11 people who are either Ethiopian or Eritrean, according to the Ugandan government.
The blasts hit within 50 minutes of each other. The first one struck an Ethiopian restaurant in a neighborhood dotted with bars and popular among expatriates. Two others exploded at the rugby center.
Ugandan President Yoweri Museveni declared a week of national mourning for victims of the bombings, beginning Tuesday, according to a government statement. All flags on public buildings will be lowered to half-staff during the mourning period, the statement said.