KAMPALA, Uganda  Somalia’s most feared insurgent group, the Shabab, claimed responsibility on Monday for the coordinated bombings that killed more than 70 people in Uganda as crowds gathered to watch the final match of the World Cup.

The Shabab have been waging a relentless insurgency against Somalia’s weak transitional federal government, and they have repeatedly threatened Uganda and Burundi for contributing troops to the African Union’s effort to stabilize the country.

“We are sending a message to every country who is willing to send troops to Somalia that they will face attacks on their territory,” Ali Mohamoud Rage, a Shabab spokesman, told reporters on Monday. He added, “Burundi will face similar attacks soon, if they don’t withdraw.”

The bombs exploded at 10:30 p.m. local time on Sunday here in Kampala, Uganda’s capital, during the match between Spain and the Netherlands, striking a popular Ethiopian restaurant and a rugby field where large screens had drawn hundreds of spectators.