Gunfire and at least one explosion have been reported near a hotel and office complex in Westlands, an upscale neighborhood of the Kenyan capital, Nairobi.

The Somali militant group al-Shabaab has claimed responsibility for the attack which began shortly after 3 p.m. (1200 GMT) on Tuesday, January 15.

“We are currently conducting an operation in Nairobi” an al-Shabaab spokesperson told al Jazeera.

According to journalist Harun Maruf, the group claimed responsibility via an affiliate account.

Nairobi police commander Philip Ndolo said they had cordoned off the area around the dusitD2 hotel off Riverside Drive, Reuters reported.

Inspector General of Police Joseph Boinnet said a number of people were injured and “criminals” could still be holed up inside the hotel.

Police suspect the incident is a terrorist attack, Boinnet told reporters.

The operation is ongoing, he said.

BREAKING: Police confirm terrorist attack at 14 Riverside. pic.twitter.com/12EwdTRS17 — Citizen TV Kenya (@citizentvkenya) January 15, 2019

Boinnet later said that the incident began “in a coordinated fashion and began at I&M Bank with an explosion that targeted three vehicles in the parking lot, and a suicide explosion in the foyer of Dusit hotel.”

Specialized units were on-site at 14 Riverside Drive to engage the attackers, the National Police Service said.

“All police teams have been dispatched to the scene where the incident is. As of now we are treating it as anything, including the highest attack,” AFP earlier reported Owino as saying.

“We wish to confirm that there has been an attack incident along 14 Riverside Drive. The area has since been cordoned off,” the Kenyan police service tweeted.

Images and video posted to social media purported to show the aftermath of an explosion and what sounded like gunshots.

‘Terror attack’ unfolding at Kenyan luxury hotel complex in Nairobihttps://t.co/USChgMR2kD pic.twitter.com/wgUqapkGks — ITV News (@itvnews) January 15, 2019

The Wall Street Journal reported a senior Nairobi-based diplomat as saying that Kenyan intelligence officials had identified six people participating in the attack.

Police said they detonated a car packed with explosives outside the complex and officers had moved away from other vehicles suspected of having explosives, the Associated Press reported.

Al-Shabaab attacks

Al-Shabaab is fighting to overthrow the internationally backed government in Somalia, but has also carried out attacks in neighboring Kenya, which has deployed troops as part of the African Union Mission in Somalia.

U.S. forces partner with Somali national security forces in counterterrorism operations, and have conducted frequent raids and drone strikes on al-Shabaab training camps throughout Somalia. Africom also works with AMISOM on both advise-and-assist missions as well as air support missions to target al-Shabaab.

In August, the U.S. Department of Defense assessed there to be between 3,000 and 7,000 al-Shabaab fighters and 70 to 250 Islamic State Somalia fighters in the Horn of Africa nation.

In September 2013, al-Shabaab militants attacked the Westgate Mall in the Westlands neighborhood of Nairobi.

The al-Qaeda linked group claimed responsibility for the attack in response to Kenyan troops’ presence in Somalia.

At least 67 people were killed and more than 150 others were injured.

Tuesday’s attack comes as one of the four Somali suspects thought to be involved in the Westgate attack was released due to lack of evidence and three others were charged, Voice of America reported.

In April 2015, al-Shabaab attacked Garissa University College, close to Kenya’s border with Somalia, killing 148 people, mostly students, and injuring another 79.