A suicide bomber detonated explosives outside a hotel in a popular beachfront area in Somalia’s capital, Mogadishu, before gunmen stormed the building, setting off a four-hour siege that left at least 32 people dead and more than 60 others wounded, the police said on Saturday.

The Islamist militant group Al Shabab claimed responsibility for the deadly assault, which started late Friday. Al Shabab have been waging an insurgency against the internationally backed government in Somalia for more than 17 years and have previously targeted the beach area, Lido, which is popular with businesspeople and officials as well as with other residents.

A witness, Mohamed Jibril, said that, at the time of the attack, he had been out with friends in the area, which had been thronged with hundreds of people.

“We heard a loud explosion followed by gunfire,” Mr. Jibril said in an interview.

“I have never seen anything like that in my entire life,” he added. “I saw many people lying on the beach asking for help, and no one dared to help them because there was ongoing shooting.”

A spokesman for the Somali police, Abdifatah Adan Hassan, said that officers had killed three attackers who had stormed the beachfront hotel, ending the siege.

“Our security forces have eliminated all three Shabab attackers who entered the hotel and took hostage the customers and beachgoers who took shelter inside the building,” he said.

The attack underscores Al Shabab’s enduring threat despite yearslong efforts by the Somali government and its allies, including the United States and the African Union, to suppress the militant group.

President Hassan Sheikh Mohamud of Somalia vowed to defeat Al Shabab when he came to power in 2022, and his efforts initially proved successful as the government limited the group’s ability to carry out attacks in the capital and kicked the militants out of large swaths of the country.

But in the past year, Al Shabab, which is linked to Al Qaeda, have succeeded in retaking villages and towns across central and south-central Somalia. In January, Al Shabab also captured a United Nations helicopter with at least nine people onboard after the craft made an emergency landing in an area controlled by the group.

In a post on social media, Mr. Mohamud sent his condolences to the families of those killed in the latest outbreak of violence.

“The terrorist attack on Lido beach shows the brutality” of the attackers “and their aim to kill the Somali people everywhere,” he said in a statement, adding, “The government is committed to eradicating this group from the whole country.”

The Lido area has been the target of several previous attacks, including a six-hour siege by Al Shabab on a beachside hotel in 2023, which left six civilians dead and 10 wounded. Five people were killed in a car bomb blast at a cafe in the capital last month. And in March, the militants killed three people and wounded 27 in an hourslong siege of another Mogadishu hotel, breaking a relative lull in the fighting.