Karachi - Heavily armed militants launched an assault on Pakistan's busiest airport in the southern city of Karachi, leaving at least 21 dead including 10 militants in a six-hour siege that the army quelled at dawn.
Explosions and gunfire rang out as the attackers, some dressed in military uniforms, battled security forces in one of the most brazen attacks in years on Pakistan's biggest city.
Authorities said all 10 militants had been killed and that at least 11 dead bodies including security personnel and two civilians were received by the city's main Jinnah Hospital.
"Update: Area cleared. No damage to aircraft, fire visible in pics was not plane but a building, now extinguished. All vital assets intact," military spokesperson Major General Asim Bajwa said in a tweet.
The assault forced the closure of the Jinnah International Airport but Bajwa said it would be ready to resume services later in the day.
The attack will raise fresh concerns about Pakistan's shaky security situation, and questions about how militants were able to penetrate the airport which serves one of the world's biggest cities.
No one has yet claimed responsibility for the assault, but it came as talks between Pakistan and the Taliban which began earlier this year hit an impasse.
Officials said the gunmen entered from at least two sides of the airport at around 23:00 on Sunday - the terminal used for the hajj pilgrimage and an engineering section close to an old terminal that is no longer in use.
Armed with guns, grenades and rocket launchers, they clashed with the airport's security force, police, paramilitaries and later commandos.
Smoke was seen billowing from the airport as fires raged close to planes parked on the runway.
'I saw the terrorists firing'
An AFP reporter at the airport witnessed three "huge" blasts, in what intelligence officials at the scene said they believed were suicide bombers detonating their explosives.
Broken glass and spent gun magazines littered the engineering section where the first exchange of gunfire took place as smoke from grenade attacks began to die down.
"I heard fierce firing and then saw the terrorists firing at security forces. I don't know a lot more than that," said eyewitness Sarmad Hussain, an employee of national carrier Pakistan International Airlines (PIA).
"Thank God I am alive, this is very scary," he told AFP.
Syed Saim Rizvi, who was on board a plane on the runway, tweeted: "Huge blast!!!! I do not know whats going on outside - heavy firing started again - full panic on board!"
The director of the city's main Jinnah Hospital, Seemi Jamali, said that 11 dead bodies including nine security personnel and two civilians had been brought in, along with the partial remains of two other unidentified bodies.
Another 21 people were wounded, he told AFP.
A spokesperson for PIA, Mashud Tajwar, said that two domestic flights bound for Karachi had been diverted to nearby airports.
There has so far been no claim of responsibility for Sunday night's incident but similar raids in the past have been claimed by Taliban militants who rose up against the Pakistani state in 2007 in an insurgency that has claimed thousands of lives.
Taliban gunmen attacked the Mehran naval base in 2011, which is three kilometres from the airport, destroying two US-made Orion aircraft and killing 10 personnel in a 17-hour siege.
Taliban and other militants in uniform carried out a similar raid at Pakistan's military headquarters in the garrison city of Rawalpindi in 2009, leaving 23 dead including 11 troops and three hostages.
The raid will cast attention on the government's controversial decision to negotiate with the Taliban instead of using greater force to deal with them.
Prime Minister Nawaz Sharif's government began negotiations with the umbrella militant group Tehreek-e-Taliban Pakistan (TTP) in February, with a ceasefire beginning 1 March but breaking down a month later.
The TTP emerged in response to a raid on a radical mosque in Islamabad, but Islamist violence in the country began to surge in 2004 following the army's deployment in volatile tribal areas.
Attack on Shi’ite pilgrims
In a separate attack in southwest Baluchistan province late Sunday, at least 23 people including several Shi’ite pilgrims were killed in a gun and suicide assault on the restive Pakistan-Iran border.
The attack came when a bus carrying Pakistani pilgrims returning from a visit to holy Muslim sites in Iran stopped at a restaurant in the Pakistani town of Taftan, around 700km southwest of the provincial capital Quetta.
Provincial home secretary Akbar Durrani said four suicide bombers attacked two restaurants full of pilgrims.
One suicide bomber was shot dead trying to enter one of the restaurants while the other three managed to enter a second restaurant and blow themselves up.
As well as the Taliban threat, Pakistan is facing a rising tide of sectarian bloodshed mainly targeting minority Shi’ite Muslims.