Two Chinese nationals were killed in an explosion near the international airport of the southern Pakistani city of Karachi on Sunday night, the Chinese embassy in Pakistan said, in what it described as a "terrorist attack", Reuters reported.

In a statement emailed to journalists, separatist militant group Baloch Liberation Army (BLA) claimed the explosion was an attack carried out by them using a vehicle-borne improvised explosive device targeting Chinese nationals, including engineers.

Pakistan broadcaster Geo News reported at least 10 people were injured in the blast in addition to some fatalities. The nature of the blast was not immediately clear, Geo News cited a provincial official as saying.

Karachi police did not immediately respond to request for comment.

The Chinese embassy said a convoy from the Port Qasim Electric Power Company was attacked near the airport, read the report.

"The Chinese Embassy and Consulates General in Pakistan strongly condemn this terrorist attack, express deep condolences to the innocent victims of both countries and sincere sympathies to the injured and (their) families," the statement said, adding the Chinese side has been working with Pakistani authorities in the aftermath.

The BLA seeks independence for the province of Balochistan, located in Pakistan's southwest and bordering on Afghanistan and Iran. In August, it launched coordinated attacks in the province, in which more than 70 people were killed.

BLA specifically targets Chinese interests - in particular the strategic port of Gwadar on the Arabian Sea, accusing Beijing of helping Islamabad exploit the province. It has previously killed Chinese citizens working in the region and attacked Beijing's consulate in Karachi, Reuters reported.

Over 80 police personnel have been injured in clashes with supporters of jailed former Prime Minister Imran Khan taking part in a march near Islamabad, Interior Minister Mohsin Naqvi said on Saturday.

The march, which is being led by the head of the northwestern province of Khyber-Pakhtunkhwa, where Khan's party remains in power, aims to gather in the capital, defying a ban on congregations, to press for Khan's release and agitate against the ruling coalition, Reuters reported.

"The convoy, led by the chief minister, fired on the police and continuously used teargas against law-enforcers," Naqvi told journalists.

He said more than 80 police officers had been treated for injuries since Friday, when clashes broke out just outside the city during an anti-government rally.

Authorities have sealed off Islamabad and blocked cellphone services to prevent the gathering, read the report.

Islamabad is on high alert ahead of a series of top-level diplomatic events scheduled over the next two weeks, including a visit by India's Foreign Minister Subrahmanyam Jaishankar.

Naqvi said while the convoy was heavily armed, the police had been instructed not to carry weapons to prevent the situation from escalating. The government has deployed the army to enhance security in Islamabad.

Khan's Pakistan Tehreek-e-Insaf (PTI) party denies using violence, and says it wants to hold a peaceful gathering.

Naqvi had previously called on the PTI to delay any gathering until after diplomatic engagements in the city, including a Shanghai Cooperation Organisation (SCO) meeting on Oct. 15-16 which will be attended by delegations, including from China, Russia and India.

On Saturday, Naqvi said the authorities had intelligence that the protesters planned to disrupt the SCO conference in a bid to gain attention.

"We can't allow this. I will say to them again, to not cross more red lines - don't make us take extreme steps," Naqvi said.

The PTI, which says the Islamabad protest is just for one day, is also holding a gathering in the eastern city of Lahore on Saturday, where a lockdown of roads is in place, Reuters reported.