Pakistani army commandos say they have surrounded seven heavily armed militants who attacked a terminal used by VIPs at the main airport in Karachi.
At least six attackers already have been killed along with at least six airport security personnel.
Officials say all passengers have been evacuated to safety, and flights in and out of the airport are suspended.
The militants used hand grenades and rocket launchers to try to blast their way into the Jinnah terminal.
Security officials say some of the militants wore uniforms that resembled airport security uniforms. They were reported wearing explosives.
Prime Minister Nawaz Sharif has condemned the attack.
No one has claimed responsibility, but Pakistani officials called the gunmen “terrorists” who appeared to be on what they called a "die and kill mission."
Hours earlier Sunday, suspected Sunni Muslim militants killed at least 23 people during a suicide attack on buses carrying Shi'ite pilgrims in the town of Taftan, in Baluchistan province on the border with Iran. Baluchistan's home minister, Sarfaraz Bugti, says security forces killed one bomber while three others blew themselves up.