The Pakistani Taliban have said they were behind an attack at the country's largest airport that killed at least 28 people, including 10 militants.
The raid happened late on Sunday at a terminal used for cargo and VIP flights at Karachi international airport.
Fresh violence reportedly broke out early on Monday, hours after the army said it had retaken control and all 10 attackers had been killed.
Karachi has been a target for many insurgent attacks.
Shahidullah Shahid, a Taliban spokesman, was quoted as saying by Reuters on Monday: "It is a message to the Pakistan government that we are still alive to react over the killings of innocent people in bomb attacks on their villages."
The dead terminal staff were said to be mostly security guards from the Airport Security Force (ASF) but also airline workers. At least 14 people were wounded.
All flights are being diverted to other airports.
Analysts say the attack further undermines Prime Minister Nawaz Sharif's attempt at initiating peace talks with the Taliban.
The negotiations have made little headway since February. Critics have argued that they could allow the militants to regroup and gain strength.
Gunmen disguised as police guards kill 26 at Pakistan airport http://t.co/qm6uI5puW9
— Daily Mail Online (@MailOnline) June 9, 2014
At the scene: Riaz Sohail, BBC Urdu, Karachi
I was with police at the Fokker Gate where some of the militants initially entered - and a few hundred metres from the fighting. We spent five to six hours at the airport while the militants were battling.
— dna (@dna) June 9, 2014
Witnesses told us the militants came in a high-roofed van, which dropped them at the entrance to this terminal and then quickly left.
We were told several militants jumped into the buildings and shortly afterwards a very heavy deployment of the Pakistani army arrived and firing began.
— Global Voices (@globalvoices) June 9, 2014
We took cover while loud bomb blasts could be heard. Officials told us it was suicide bombers detonating their vests. Later they discovered live suicide jackets from militants shot dead in the encounter.
Their intention may well have been for a longer and deadlier siege as one official told me that the militants had brought dry food supplies with them.
— Gulf News (@gulf_news) June 9, 2014
The army said the 10 gunmen stormed Jinnah International Airport in two teams of five on Sunday at 23:00 local time (18:00 GMT).
The attackers are believed to have entered the area using fake ID cards, although some reports suggest they cut through a barbed wire fence.
— Mashable (@mashable) June 9, 2014
They threw grenades and fired at security guards in the old terminal, which is now only used for cargo and VIP operations.
The Chief Minister of Sindh province, Qaim Ali Shah, said the attackers "were well trained".
"Their plan was very well thought out," he said, adding that they had failed to destroy some of the aircraft as they had intended.
Seven of the attackers later shot dead during a gun battle which lasted until about 04:30. Another three detonated their explosives.
The attackers set fire to cargo, but no aircraft were damaged, the officials said.
Army officials said there were indications that some of the gunmen may have been foreign nationals.
There were also reports of at least two huge blasts at the airport.
Sarmad Hussain, an official with Pakistan International Airlines, told the Associated Press news agency: "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.