This article is more than 6 years old

This article is more than 6 years old

At least 25 people have been killed in a suspected terrorist attack in the Kenyan capital, Nairobi, after gunmen opened fire and threw grenades in an upmarket shopping centre.

On Saturday evening the Kenyan presidency tweeted that one of the gunmen had been arrested. The country's head of police, David Kimaiyo, said several assailants were also apprehended when police and military entered the mall following the attack.

Witnesses said the men, brandishing AK-47s, told Muslims to leave and shot those they believed were non-Muslims.

"We are treating this as a terrorist attack," said the police chief Benson Kibue, adding that 10 attackers were involved. Police did not say which group was responsible.

A wounded woman is helped to safety after gunmen opened fire in a shopping centre in Nairobi, Kenya. Photograph: Simon Maina/AFP/Getty Images

"It is a possibility that it is an attack by terrorists, so we are treating the matter very seriously," Mutea Iringo, the principal secretary in the ministry of interior, told Reuters.

The al-Qaida linked Somali Islamist militant group al-Shabaab has not formally claimed responsibility for the attack, but used it's official Twitter handle, @HSM-Press, to describe the killings as "a very tiny fraction of what Muslims in Somalia experience at the hands of Kenyan invaders".

The group also accused the Kenyan government of continuing to "massacre innocent Muslims in Somalia", a reference to Kenyan troops being sent into Somalia in 2011 in order to fight al-Shabaab.

HSM Press Office (@HSM_Press) The Kenyan government, however, turned a deaf ear to our repeated warnings and continued to massacre innocent Muslims in Somalia #Westgate

The ministry earlier posted warnings to the public on Twitter to avoid the area around the Westgate centre, the most exclusive shopping centre in the city.

Elijah Kamau told the Associated Press the gunmen had made the statement about Muslims as they began their attack.

A Kenyan woman is carried away from the shopping centre. Photograph: Simon Maina/AFP/Getty Images

The interior ministry asked local media not to televise the gun battle live because the gunmen were watching the screens in the shopping centre.

Armed police arrived nearly half an hour after the attack began and engaged the gunmen in a shootout. Officers shouted: "Get out, get out", and scores of shoppers fled the building. At least half a dozen were bloodied and helped by first-aiders.

Security guards used shopping trollies to wheel out several wounded children and at least one man.

Rob Vandijk, who works at the Dutch embassy, said he was eating at a restaurant in the shopping centre when attackers lobbed grenades inside the building. He said gunfire then burst out and people screamed as they dropped to the ground.

A former British soldier said: "I personally touched the eyes of four people and they were dead. One of them was a child. It's carnage up there."

Cars were left abandoned outside the centre, which is located in the city's affluent Westlands area and is frequented by expatriates and wealthy Kenyans.

Other witnesses said that they had seen about five armed assailants storm the shopping centre and that the incident appeared to be an attack rather than an armed robbery.

"They don't seem like thugs. This is not a robbery incident," Yukeh Mannasseh told Reuters. "It seems like an attack. The guards who saw them said they were shooting indiscriminately."

Kenya has seen a rise in terrorist attacks and threats in recent years, some of which are believed to be in retaliation for a military crackdown on al-Shabaab. The group vowed in 2011 to carry out a large-scale attack in Nairobi in retaliation for Kenya sending troops into Somalia to fight them.

The attacks often involve gunmen armed with automatic weapons and grenades, and their targets include bars, nightclubs and restaurants in various parts of the country. A suspected al-Shabaab attack in January left five people dead and three injured at a restaurant in the eastern city of Garissa. In August last year one person was killed and six injured in the Eastleigh area of Nairobi on the eve of a visit by Hillary Clinton, the then US secretary of state.

Last month 18 of the 19 US embassies and consulates across the Middle East and Africa were closed after a message between al-Qaida officials about plans for a major terrorist attack was intercepted.