Two Chinese nationals were killed in an explosion near the international airport of the southern Pakistani city of Karachi on Sunday, the Chinese embassy in Pakistan said, Reuters reports. They worked for a power plant, Pakistan's finance minister said on Tuesday.

It was the most serious attack against Chinese nationals in Pakistan since a suicide bomber killed five Chinese engineers working on a hydropower project in March, which prompted Beijing to call on Islamabad to implement more stringent security measures.

The Chinese embassy in Islamabad and Pakistan's foreign ministry have described Sunday's blast as a "terrorist attack." In a statement emailed to journalists, separatist militant group Baloch Liberation Army ( BLA ) claimed the explosion was a suicide attack carried out by them, using a vehicle-borne bomb.

Pakistani media have reported that nearly a dozen people were injured in the blast.

A top security official in Islamabad told Reuters on condition of anonymity that the latest attack was a security failure and that all senior staff responsible for Chinese security in Karachi had been removed from service.