The attack on Jinnah International Airport in Karachi, Pakistan's sprawling commercial hub of 18 million people, took place as Prime Minister Nawaz Sharif's government tries to engage Pakistani Taliban militants in negotiations to end years of fighting.
Gun battles went on for several hours and television pictures showed fire raging at the airport as ambulances ferried casualties away, but by dawn on Monday, the army said the airport had been secured.
"(The attackers) were confined to two areas and eliminated," the Dawn newspaper cited military spokesman Major-General Asim Bajwa as saying.
There was no immediate claim of responsibility, but Pakistani Taliban militants, allied with but separate from the Afghan Taliban, are battling to overthrow the Pakistani state and impose their hardline vision of Islamist rule.
Earlier, officials said all flights had been diverted.
Peace talks between the government and the Pakistani Taliban have failed in recent months, dampening hopes of reaching a negotiated settlement with the insurgency, which continues attacks against government and security targets.
Jinnah International Airport attack: 23 dead including 10 militants killed
(PTI) At least 23 persons, including 10 terrorists have been killed when heavily armed militants attacked the Jinnah International Airport's old terminal in Pakistan's financial capital Karachi.
The terrorists were corned and killed after they attacked the old airport terminal building late last night, posing as Airport Security Force (ASF) personnel.
"All 10 terrorists have been killed, the airport secured and they were unable to damage any aircraft or installations," a spokesman of the Inter Services Pubic Relations (ISPR) said.
He said that army units from the nearby Malir cantonment base, ASF commandos, paramilitary rangers and police had carried out the joint operation to clear the old airport area.
Sophisticated machine guns and rocket launchers were recovered from the terrorists who were being identified, the spokesman said.
For nearly six hours the Jinnah international airport which is close to the old airport terminal was shut down and all flights diverted as exchange of gunfire took place and heavy plumes of smoke and fire could be seen rising from inside the runaway area where the terrorists took cover in the hanger and engineering workshops.
During the ordeal several loud explosions were also heard but the spokesman confirmed that no aircraft was damaged nor any important assets or installations damaged during the operation.
Till the filing of this report no one had claimed responsibility for the attack.
Sagheer Ahmed, the Sindh minister for health, told reporters that 13 people lost their lives in the terrorist attack.
"Those martyred include the ASF personnel, civilian engineers and personnel of CAA and PIA and a police officer while a dozen have also been injured and are admitted to hospital," he said.
Defence minister, Khawaja Asif described the attack as cowardly and said it was another example of how terrorists were trying to destroy important installations and locations of the government.
"But I can tell you these terrorists will not succeed in their aims and will be defeated," Asif said.
The attack was reminiscent of the deadly attack carried out by some 15 militants of the Tehreek-e-Taliban in May, 2011 on the Mehran naval airbase here in which the attackers killed some 18 personnel and damaged aircrafts before being killed in a counter attack.
The attack came days after a peace process between the Tehreek-e-Taliban broke down and a ceasefire announced by the TTP was called off.
Since then than there has also been a major break in the TTP with the powerful Mehsud group announcing their separation from the militant outfit led by Maulana Fazlullah.
The Mehsud group commanders had warned of resuming attacks against the government and security personnel and installations.
Immediately after the daring attack all flight operations were suspended from the Jinnah international airport with flights not taking off and those scheduled to land in Karachi were diverted to Nawabshah and Quetta or turned back to their original destinations.
Police sources said that the heavily armed terrorists dressed in ASF uniforms forced their way into the old terminal building from two gates and caught the security personnel on duty unaware.
Security forces including Military troops, ASF and police commandos surrounded a hanger and workshop near the old terminal where the terrorists took control after entering the runaway from the old terminal building.