ISLAMABAD (AP) — A car bomb aimed at a Pakistani Shiite politician missed him but killed four other people Tuesday, hours after police defused an explosives-laden vehicle near the house where ex-leader Pervez Musharraf is being held, in the latest signs of simmering unrest in the country.

Police in the capital were investigating how a car with a bomb inside managed to approach Musharraf's house. It was found parked about 150 meters (500 feet) from the main gate of Musharraf's house on the outskirts of the city, said Islamabad police chief Bani Amin. The former military strongman was home at the time.

Musharraf is being held under house arrest in connection with a case involving his decision to fire senior judges while in power.

Musharraf seized power in a military coup in 1999 when he was army chief but was forced to step down in 2008 because of growing discontent with his rule. He returned last month to make a political comeback, but his fortunes have gone from bad to worse since then.

He was met with paltry public support and a raft of legal challenges, including the case that has him under house arrest. He has been barred from running in the May 11 parliamentary election for which he returned.

On the eve of his arrival, the Taliban issued a video saying they had put together a special group of militants to kill Musharraf. He was attacked several times while he was in power, but he managed to escape unharmed.

The Taliban have targeted Musharraf because of his alliance with the United States in fighting Islamic militants while in power and for his decision to launch a raid in 2007 on a mosque in downtown Islamabad that had become a sanctuary for militants opposed to Pakistan's support for the war in Afghanistan. At least 102 people were killed in the weeklong operation, most of them supporters of the militants.

The car bombing in southwestern Pakistan on Tuesday hit Quetta, the capital of Baluchistan province. The bomber targeted Abdul Khaliq Hazara, head of the Hazara Democratic Party, said police officer Fiyaz Sumbal. The Shiite politician was not harmed, but four people were killed and 26 wounded, said Sumbal. The dead were two paramilitary soldiers and two passers-by.

Sunni Muslim militants in Pakistan have increasingly targeted minority Shiites, whom they consider heretics, especially in Baluchistan.

Elsewhere in Quetta, four small bombs exploded in different commercial areas of the city, wounding 12 people, said Sumbal.

In the southern city of Karachi, unknown assailants threw a homemade bomb at an election office run by the Muttahida Quami Movement, killing two people and wounding eight, police officer Amir Farooqi said. The party has been threatened by the Taliban in the run-up to the election.

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AP writers Abdul Sattar in Quetta, Pakistan and Atif Raza in Karachi, Pakistan contributed to this report.