Motorcycle-riding gunmen ambushed a car carrying a senior Pakistani jail official in this southern port city on Thursday, killing him and four others, police said.

In other violence, a roadside bomb blast killed a Pakistani soldier and wounded five in a northern tribal region, just hours after a land mine exploded in the same area wounding two more troops. Retaliatory fire from soldiers killed a woman passer-by.

Suspected militants also shot dead a paramilitary soldier in the southwest, while two civilians died in a separate land mine blast.

CountryWatch: Pakistan

The Karachiassailants, riding on at least four motorcycles, sprayed gunfire at the car of Amanullah Niazi, deputy superintendent of the Karachi Central Prison, and an accompanying van carrying jail guards, said senior police official Sanaullah Abbasi.

Niazi, his driver and two bodyguards were killed in the car while the jail official's brother was seriously wounded, Abbasi told The Associated Press.

A passer-by was shot dead in the crossfire while two others were wounded, Abbasi said. Three jail guards in the van were also wounded, including one seriously.

No details were immediately available on the killers, who fled.

The motive for the attack was unclear, but Rauf Siddiqi, home minister of Sindh Province of which Karachi is the capital, said the prison official had received death threats in the past.

"It is sheer terrorism. He was under threat and we will investigate those quarters from where he was receiving threats," Siddiqi said without saying who had threatened Niazi nor why.

Niazi's jail holds dozens of prisoners convicted in sectarian killings and bombings, some of whom had quarreled with the targeted official for allegedly favoring other inmates, a senior prison officer said on condition of anonymity as he was unauthorized to talk to the media.

Niazi's assassins fired at his car as it waited at traffic lights in a southern neighborhood of Karachi, Pakistan's largest city, said witness Nazir Ahmed. Security officers returned fire.

The inside of Niazi's car was splattered with blood and its windows shattered, officials said. Police found one motorcycle at the scene believed to have been left by the attackers.

The roadside bomb that killed a Pakistani soldier and wounded five happened near Sra Shakara, a village in the North Waziristan tribal area, a security official said.

Earlier near North Waziristan's main town of Miran Shah, a land mine wounded two soldiers, prompting other troops to fire at people fleeing the scene, killing one woman dead and wounding two farmers, another official said.

In southwestern Baluchistan province, assailants shot dead a paramilitary soldier fetching water near the town of Kohlu, said local government official Komail Ali.

Elsewhere in Baluchistan, two civilians died when their motorcycle hit a land mine near Sui, a town where rebel tribesmen plant land mines to target security forces, police said.

Earlier, assailants lobbed a grenade into a residence for security officials in Baluchistan, wounding three, police said.