Police in Pakistan said Tuesday three Chinese nationals and their local driver were killed in a suicide bombing of a van in the southern city of Karachi.
Senior police officers told reporters the victims had been traveling to the city's Chinese-built Confucius Institute when the blast hit their van at the entrance.
Those killed included the director of the institute, which offers Chinese language graduate classes, and two female teachers. Also killed was their Pakistani driver. Another Chinese national was injured in the attack.
Ghulam Nabi Memon, the Karachi police chief, said the blast might have been the work of a suicide bomber but an investigation was underway. He noted that an initial review of closed-circuit video from the site showed that a person dressed in a black burqa walked up to the van just before the explosion.
Local television channels later aired footage showing a female attacker detonating the bomb as the slow-moving van was entering the institute.
An outlawed separatist group known as the Baluch Liberation Army reportedly took responsibility for the bombing, saying a woman carried out the attack.
It was not immediately possible to verify the militant group's claims from independent sources.
The Pakistani Foreign Ministry condemned the Karachi attack as a "reprehensible terrorist" act.
"The cowardly incident is a direct attack on the Pakistan-China friendship and ongoing cooperation. Pakistan and China are close friends," a ministry statement said.
Later Tuesday, in a video message sent to reporters, a masked BLA commander claimed that his group has formed a "special unit" to target Chinese officials and installations to ensure CPEC (China-Pakistan Economic Corridor) projects "will fail miserably" in Baluchistan.
"President Xi Jinping, you still have time to quit Baluchistan, or you will witness a retaliation from Baluch sons and daughters that you will never forget," warned the militant commander while addressing the Chinese leader.
The BLA had taken credit for staging a 2018 gun and bomb attack against the Chinese consulate in Karachi that killed two Pakistani security guards.
The militant group, along with other Baluch separatists, operate mainly out of Pakistan's southwestern Baluchistan province. The militants are opposed to Beijing's economic investments under the multibillion-dollar CPEC.
The CPEC, an extension of Beijing's Belt and Road initiative, has built roads, power plants and the deep-water Gwadar port in Baluchistan.
Pakistan accuses rival India of supporting and funding Baluch militants to undermine CPEC, charges that New Delhi rejects.
In February, the BLA attacked two Pakistani army bases in Baluchistan, and the ensuing clashes lasted three days, killing nine soldiers and 20 assailants.
BLA militants tried to storm the Karachi Stock Exchange building in 2020, where a Chinese consortium has a 40% stake, but security forces engaged the assailants in the parking area and killed all of them.
The insurgent group is designated as a terrorist organization by Pakistan and the United States.
"Pakistan remains the most dangerous place for overseas Chinese workers, which is a real problem," tweeted Adam Weinstein, a research fellow at the U.S.-based Quincy Institute for Responsible Statecraft.
In July, a suicide car bombing of a bus convoy transporting Chinese workers to a China-funded Dasu hydropower project under construction in the northern region of Kohistan killed nine of the workers and three security guards. It was the largest loss of life of Chinese nationals in Pakistan.