A bomb blast has ripped through a passenger van carrying Chinese nationals in the southern Pakistani port city of Karachi, killing three of them and a Pakistani national.
The Baloch Liberation Army (BLA) separatist group claimed responsibility for the blast, which took place on Tuesday near a university campus, adding in an email sent to a Reuters reporter that it had been carried out by a female bomber.
The blast was the first major attack against Chinese nationals in Pakistan since last year when a 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 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.
The BLA attacked two army bases in southwestern Balochistan province earlier this year, killing seven soldiers, and it lost 13 of the attackers in an hours long gun-battle with Pakistan army.
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.