Heavily armed gunmen have attacked Karachi international airport in Pakistan, killing 13 people.

An army spokesman said all 10 of the gunmen who attacked Jinnah International Airport's old terminal had also been killed.

Army commandos were called in, and gunfire lasted for more than five hours before the airport was secured.

But all operations at the terminal remain suspended and all flights are being diverted to other airports.

Staff and passengers were evacuated.

At least 14 people were wounded.

Billowing smoke

The dead terminal staff were said to be mostly security guards from the Airport Security Force (ASF) but also airline workers.

Dawn News said the gunmen had infiltrated from the Fokker Gate area.

The attackers are believed to have entered the area using fake ID cards. Other reports suggest they cut through a barbed wire fence.

There is no indication yet who carried out the attack.

Smoke was seen billowing from the terminal.

'Plane on fire'

An ASF spokesman earlier told Agence France-Presse that the gunmen had reached the runway and that a "gun battle is continuing between terrorists and [armed] forces".

There were also reports of at least two huge blasts at the airport.

Hammad, a diplomat staying near the airport, told the BBC he had gone on to his rooftop and could see a plane on fire in the airport.

The army later said no aircraft was damaged and that a fire at an oil facility was brought under control.

Sarmad Hussain, an official with Pakistan International Airlines, told AP: "I was working at my office when I heard big blasts - several blasts - and then there were heavy gunshots."

He said he and a colleague escaped by jumping from a window. His colleague broke a leg.

The terminal is not normally used for commercial flights but for cargo and special VIP operations.

Pakistan has been fighting an Islamist insurgency for more than a decade, with the Pakistani Taliban the main militant group.

Pakistan's Prime Minister Nawaz Sharif recently told the BBC he was still hopeful his peace initiative with the Taliban could succeed.

But little headway has been made since February and there have been frequent violent clashes.

Karachi has been a target for many insurgent attacks.

Gunmen attacked the Mehran naval base there in 2011, killing 10 personnel and destroying two aircraft in a 17-hour siege.