KARACHI: Two Chinese nationals were shot at and injured on Tuesday in Pakistan’s commercial hub of Karachi, police and hospital officials said, after a string of attacks that spurred Beijing to demand tougher security for its citizens.

Faizan Ali, a senior superintendent of police, said two Chinese nationals had been shot, but gave no further details.

A spokesperson for Liaquat National Hospital in the southern port city said it was treating the two, one of whom was in serious condition.

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It was not immediately clear who was responsible or if militant violence was behind the attack, one of several that have prompted Beijing to urge Pakistan to roll out more stringent security measures for its citizens.

Chinese engineers have been working on a number of projects in Pakistan with Beijing investing over $65 billion in infrastructure as part of the China-Pakistan Economic Corridor (CPEC) under its wider Belt and Road initiative.

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Chinese nationals have previously come under attack by several militant groups in Pakistan.

In October this year, a bombing near Karachi’s international airport killed two Chinese engineers.

In a statement emailed to journalists, the 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, according to Reuters.