A bomb blast ripped through a passenger van carrying Chinese nationals in the southern Pakistani port city of Karachi on Tuesday, killing three of them and a Pakistani, police said.
The Baloch Liberation Army (BLA) separatist group claimed responsibility for the blast, which took place near a university campus, adding in an email sent to a Reuters reporter that it had been carried out by a woman suicide bomber.
The blast was the first major attack against Chinese nationals in Pakistan since last year when a suicide bomber blew up a passenger bus in northern Pakistan that killed 13 people, including nine Chinese.
Tuesday's attack on citizens of longtime ally China appears to be the first big challenge for newly elected Prime Minister Shehbaz Sharif, who expressed grief and sorrow over the loss of the Chinese nationals.
Karachi police chief Ghulam Nabi told reporters the blast killed three foreigners and a local.
"The reports we have got is that they're Chinese," he said in comments telecast live from the scene of crime. He said the three Chinese were teachers at Karachi University.
Baloch separatist guerrillas, who say they are fighting for a greater share in regional resources of mines and minerals, usually attack gas projects, infrastructure and the security forces.
They also attack Chinese projects, and occasionally kill Chinese workers despite Pakistani assurances that it is doing everything it can to protect the projects.