Two Chinese nationals were wounded on Tuesday by a security guard who opened fire at a garment factory in Pakistan's commercial hub Karachi, in the latest in a string of attacks that have spurred Beijing to demand better security for its citizens.

Large contingents of police were deployed at the site of the factory in Karachi's industrial area, and forensic teams could be seen entering the premises, which had been cordoned off.

There was no immediate claim of responsibility and no official confirmation of the details of the incident. Senior superintendent of police Faizan Ali told Reuters that the Chinese nationals had been shot at, but gave no further details.

One police official told Reuters on condition of anonymity that the shooting had been carried out by a security guard. The guard had not yet been arrested and it was difficult to ascertain the motive for the shooting, the official said.

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

The attack follows other incidents including a bombing near Karachi's international airport that killed two Chinese engineers last month, which was claimed by separatist militant group the Baloch Liberation Army (BLA).

China has stepped up longstanding demands for better security for its citizens in Pakistan. Ambassador Jiang Zaidong told a gathering in Islamabad last month that the rising number of deadly attacks was unacceptable.

The Pakistan foreign office responded that Islamabad was fully committed to providing security for Chinese nationals, projects and institutions. It said in a statement on Oct. 31 that the commitment had been conveyed at the highest levels of the Chinese government.

A decades-long insurgency in the southwestern province of Balochistan has led to frequent attacks against the government, army and Chinese interests. The militants say they want a greater share of regional resources.

The region is home to the deep-water Gwadar port built by Beijing as part of $65 billion in investments for the China-Pakistan Economic Corridor under President Xi's Belt and Road Initiative.