Three policemen and one civilian were killed in an attack by unknown gunmen in Kazakhstan’s commercial capital of Almaty on Monday, the Interior Ministry said, adding that one suspect had been detained and another was still at large.

During the attack killed one civilian and three police officers.

The statement gave no further details.

Kazakhstan’s National Security Committee said in a statement Monday it raised the terror threat level to red after the attack on the police station. It would not elaborate

Authorities described the violence as a terrorist attack and blamed it on radical Islamists.

Two witnesses told Reuters they had heard shots in several areas in the centre of Almaty, the mainly Muslim country’s biggest city.

“We saw a man with a rifle, he passed by,” one shop worker said by phone.

Police cordoned off several central streets, including the one near a local office of the KNB security police, where shots were also heard.

“I heard one shot, most probably, fired from a pistol,” said one man standing nearby.

Kazakhstan, an oil rich-rich nation of 18 million, is far more prosperous than its post-Soviet neighbours in Central Asia.