Heavily armed gunmen have attacked Karachi's international airport, killing at least four security guards and hurling grenades, reports say.
Pakistani media reported between four and 10 gunmen had attacked Jinnah International Airport's old terminal.
Dawn News said security personnel had surrounded the airport and sealed off roads.
All operations at the terminal have been suspended and flights are being diverted, it said.
Staff are being evacuated.
'Exchange of fire'
The security guards killed were said to be part of the Airport Security Force (ASF).
Dawn said the gunmen had infiltrated the area from the Fokker Gate using forged identity cards.
There is no indication yet who is carrying out the attack.
Geo News said two attackers were also reported dead and that smoke is billowing from the terminal.
The terminal is not normally used for commercial flights.
Senior police official Rao Muhammad Anwar told Agence France-Presse: "Exchange of fire is continuing. We don't know the exact number of the attackers."
Pakistan has been fighting an Islamist insurgency for more than a decade, with the Pakistani Taliban the main group.
Karachi has been a frequent target for militant attacks.
