Al-Shabab – the Somalia-based extremist group that carried out the 2013 Westgate Mall attack in Nairobi that left 67 people dead – claimed responsibility and said its members were still fighting inside.

“It is terrible. What I have seen is terrible,” said Charles Njenga, who ran from a scene of blood, broken glass, burning vehicles and pillars of black smoke.

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It was not clear how many attackers took part, but the bloodshed appeared to fit the pattern of attacks al-Shabbab often carries out in Somalia’s capital, with an explosion followed by a group of gunmen storming the target.

The attack left blood and glass all over, and as night fell, gunfire continued more than two hours after the first shots were heard. Several vehicles burned, sending black smoke rising over the complex, and people were carried from the scene.

Some ducked behind cars, screaming, while others took cover behind fountains and other features at the lush complex, which includes the dusitD2 hotel, along with bars, restaurants, banks and offices.

“We are aware that armed criminals are holing up in the hotel, and special forces are now currently flushing them out,” said Kenya’s national police chief, Joseph Boinnet, described the assault as a suspected terror attack.

He did not confirm any deaths and or say how many were wounded.

But a Kenyan police officer who was among the first on the scene said: “There was no time to count the dead but it is true that there are people who are dead.”

The officer, who spoke on condition of anonymity because he was not authorised to talk to the media, said that some bodies were in restaurants downstairs and that colleagues saw others in offices upstairs.

Ambulances, security forces and firefighters converged on the scene of the latest attack along with a bomb disposal unit, and vehicles were cordoned off for fear they contained explosives.

Police said they blew up a car that had explosives inside. An unexploded grenade was also seen in a hallway at the complex.

Security forces hurried out a large group of women, one of them still in curlers. Dozens of others were rushed to safety as plain-clothes officers went shop to shop in the complex. Some people held up their hands to show they were unarmed.

Al-Shabab has vowed retribution against Kenya for sending troops to Somalia since 2011. The al-Qaeda-linked group has killed hundreds of people in Kenya, which has been targeted more than any other of the six countries providing troops to an African Union force in Somalia.

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The attack immediately reminded many Kenyans of the Westgate Mall attack, when al-Shabab extremists burst into the luxury shopping centre, hurling grenades and starting a days-long siege.

On Monday, a magistrate ruled that three men must stand trial on charges they were involved in the Westgate siege. A fourth suspect was freed for lack of evidence.

The hotel complex in Nairobi’s Westlands neighbourhood is about a mile (1.6km) from Westgate Mall on a relatively quiet, tree-lined road in what is considered one of the most secure parts of the city. The hotel’s website says it is “cocooned away from the hustle and bustle in a secure and peaceful haven”.

The attack came three years to the day after al-Shabab extremists attacked a Kenyan military base in Somalia, killing scores of people.

Additional reporting by Reuters