ISLAMABAD, Pakistan — Pakistani police placed opposition leader Benazir Bhutto under house arrest today, uncoiling barbed wire in front of her Islamabad villa and reportedly roundeding up thousands of her supporters to block a mass protest against emergency rule.

Bhutto twice tried to leave in her car, telling police: "Do not raise hands on women. You are Muslims. This is un-Islamic." They responded by blocking her way with an armored vehicle.

The former prime minister had planned to defy a ban on public gatherings and address a rally in nearby Rawalpindi, where police used tear gas and batons to chase off hundreds of supporters who staged wildcat protests and hurled stones. Dozens were arrested.

Further afield, a suicide bombing at the home of a government minister in the northwestern city of Peshawar killed four people. Minister for Political Affairs Amir Muqam was unhurt.

The attack underscored the threat posed by religious extremists in this Islamic nation that President Gen. Pervez Musharraf and Bhutto are sparring over. It was cited by Musharraf as the primary reason for imposing the state of emergency last Saturday.

But most of the thousands of people rounded up countrywide since have been moderates — lawyers and activists from secular opposition parties, such as Bhutto's Pakistan People's Party. The mass detentions have fueled criticism that Musharraf — who seized power in a 1999 coup — declared the emergency to maintain his own grip on power.

Today's crackdown showed that Musharraf was not letting up on his political rivals, despite saying a day earlier that parliamentary elections would go ahead by mid-February, just a month later than originally planned. His announcement came after intense pressure from the United States, his chief international supporter.

It also dimmed prospects that Bhutto and Musharraf would soon form an alliance against Islamic extremists that Washington has pushed for.

Speaking to reporters by phone between her two attempts to escape her home, Bhutto said her supporters would "continue to fight for democracy and the rule of law." She also repeated demands that Musharraf step down as army chief by next week, when his presidential term expires.

Bhutto's decision to join in anti-government protests against Musharraf is another blow to the military leader whose popularity has plummeted this year.