ISLAMABAD, June 9 -- At least three militants were killed in exchange of fire with security personnel at the Jinnah International Airport in Pakistan's southern port city of Karachi on early Monday, prime minister office spokesman said.

The PM office spokesman told media that so far three militants had been confirmed killed in armed clashes with the security forces while seven others were cordoned off by the security personnel at the airport.

Earlier reports said that around six-15 attackers were involved in the assault, but now PM spokesman said the number of attackers are 10.

Health Minister of southern Sindh province Sagheer Ahmed said that at least six people including four personnel of Airport Security Force (ASF), all from Civil Aviation Authority and Pakistan International Airline (PIA) were killed in the attack.

"At least 13 people including eight ASF personnel were also injured in the attack," the health minister said.

Fierce exchange of fire between militant and security personnel continues at the airport premises as commandos from Pakistan army took over the charge of operation.

Inter Services Public Relations (ISPR), the mouthpiece of Pakistan army, said in a statement that the army took over the operation which is being conducted now under the supervision of Corps Commander Karachi.

Chief Minister of Sindh province Qaim Ali Shah also reached at the airport with other officials.

Prime Minister Nawaz Sharif called Director General of Rangers (a paramilitary force) and directed him to ensure safety of all the passengers at the airport.

He also directed the concerned official to speed up the operation.

The attack was launched at about 11:20 p.m. (local time) when some unknown heavily armed militants sneaked into the terminal, used for cargo and special VIP operations, by lobbing hand grenades and opening fire at the security personnel.

The attackers reportedly set two planes including a foreign cargo plane at fire while three other planes were partially damaged when the attackers fired at them during exchange of firing with the security personnel. However, PM spokesman said that no plane had been damaged so far in the attack.

The bodies and injured have been shifted to the Abbasi Shaheed Hospital.

An eyewitness said that the attackers, wearing the attire of ASF, were armed with rockets, hand grenades and automatic guns.

All the scheduled departure flights from the airport were canceled and an emergency had been imposed at the airport.

Flight operation was suspended at the airport and all flights coming to the airport were diverted to the other nearby airports of the country.

A red alert has been issued for all the airports across the country.

All the roads leading to the airport were blocked and emergency declared in the main hospitals of the city.

No group or militant organization has claimed responsibility for the attack yet.