Gunmen killed six people Thursday in a pair of attacks in southwestern Pakistan, one of which targeted local employees of a U.N. agency, officials said.

The assailants opened fire on the staff of the United Nations Food and Agriculture Organization as they were riding in a car through Baluchistan province's Mastung district, killing two people, said police officer Rustam Khan.

A member of the group's project staff and a hired driver were the two people killed, said a U.N. official on condition of anonymity because he was not authorized to talk to the media. Another staff member was wounded, he said.

There was no immediate claim of responsibility for the attack.

Baluchistan has experienced a decades-long insurgency by nationalists who demand greater autonomy and a larger share of the province's natural resources. Baluch nationalists have targeted Pakistani security forces and officials in the past, as well as aid workers helping the government.

The province is also home to many Taliban militants, allegedly including the group's leader, Mullah Omar.

Earlier Thursday, gunmen on motorcycles opened fire on a passenger van in Quetta, the capital of Baluchistan, killing four Shiite Muslims in an apparent sectarian attack, police officer Shaukat Khan said.

Ahmad Marwat, a spokesman for the Pakistani Taliban's Jundullah faction, claimed responsibility for the shooting.

"They were Shiite infidels," Marwat told The Associated Press by telephone from an undisclosed location. "We will kill them wherever we find them."

Sunni militants with links to Al Qaeda and the Taliban have carried out scores of bombings and shootings across the country against minority Shiites in recent years, especially in Baluchistan.

The Sunni-Shiite schism over the true heir to Islam's Prophet Muhammad dates back to the seventh century.