Militants have launched a deadly suicide attack on the police headquarters in Pakistan’s largest city, as the sound of gunfire and explosions rocked the heart of Karachi for several hours.

Three security force members and a civilian were killed and 18 security force members wounded, according to government officials and Ghulam Nabi Memon, police chief for the southern Sindh province where Karachi is located.

Two suicide bombers were killed and at least one blew himself up after entering the police building, officials said.

The Pakistani Taliban in a brief statement claimed responsibility.

Murtaza Wahab, a government adviser, confirmed that police and paramilitary forces in a joint operation had cleared the police building within three hours of the attack late on Friday.

“I confirm that the operation against the terrorists is over,” said Mr Wahab.

President Arif Alvi condemned the attack in Karachi, which is Pakistan’s chief commercial city, while Prime Minister Shahbaz Sharif paid tribute to security forces for the successful operation.

Earlier, TV footage showed officers surrounding the city’s central police station as residents reported the sound of explosions and gunfire.

Pakistan’s interior minister Rana Sanaullah Khan said some of the militants threw hand grenades as they tried to force their way into the police headquarters.

Pakistan has witnessed a surge in militant attacks since November when the Pakistani Taliban ended a months-long ceasefire with the government.

Pakistan’s outlawed Tehrik-e-Taliban are a separate group but are allies of the Taliban in Afghanistan, who seized power there more than a year ago as US and Nato troops withdrew.

The Taliban takeover in Afghanistan emboldened Pakistani militants, whose top leaders and fighters are hiding across the border.

The brazen assault on Karachi’s police headquarters comes two weeks after a suicide bomber disguised as a policeman killed 101 people at a mosque in the north-western city of Peshawar.

Authorities blamed the TTP for orchestrating last month’s mosque bombing and Sarbakaf Mohmand, a TTP commander, claimed responsibility for it.