Opposition leader Benazir Bhutto on Tuesday called on Pakistan's President Gen. Pervez Musharraf to resign and ruled out serving under him in a future government after she was placed under house arrest for the second time in five days. Bhutto also said it was now likely her Pakistan People's Party would boycott January parliamentary elections, and indicated that she wanted to build an alliance with other opposition leaders, including former Prime Minister Nawaz Sharif, to restore democracy. "I could not serve as prime minister with Gen. Musharraf as president. I wish I could," Bhutto said via telephone to a group of reporters from the house in Lahore where she was held to prevent her leading a protest procession. "I simply won't be able to believe anything he said to me." Her comments appeared to bury hopes of the political rivals forming a pro-US alliance against rising Islamic extremism. They had held months of talks that paved the way for Bhutto's return from exile last month to contest the parliamentary elections. Her detention sparked unrest in the southern city of Karachi. Bhutto supporters fired gun shots at two police stations in a poor district where party is popular, and police used tear gas to disperse demonstrators, senior police officer Fayyaz Khan said. No one was hurt. Bhutto told private Geo TV network that Musharraf was a hurdle to democracy and must resign both as president and army chief. She accused Musharraf of imposing effective martial law when he declared emergency rule on Nov. 3 - suspending citizens' rights and rounding up thousands of his opponents. Musharraf said the restrictions were needed to bolster the fight against the Taliban and al-Qaida. With Pakistan's political turmoil deepening, US Deputy Secretary of State John Negroponte was set to visit Pakistan this week and was expected to reiterate Washington's calls for Musharraf to lift the emergency, amid concerns that its restrictions - such as on independent media and rallies - would make it hard to hold a fair vote. US Embassy spokeswoman Elizabeth Colton said the trip was pre-planned and part of a regular strategic dialogue with Pakistan, a key ally in the US-led war on terror. Authorities mounted a massive security operation to prevent Bhutto from leading a 300-kilometer procession to the capital, Islamabad to press for an end to the emergency. Thousands of riot police blocked all roads leading to the upscale neighborhood where Bhutto was staying and police said more than 100 of her supporters had been arrested in the area Tuesday. Eight trucks and tractors loaded with sand were parked across one street. Police stood behind the vehicles and a row of metal barricades topped with barbed wire. Reporters could not see the house of a lawmaker where Bhutto was staying because they were prevented from crossing the cordon. Officers detained scores of her supporters, including two lawmakers, who approached the barricades shouting slogans including "Go Musharraf go!" and "Prime Minister Benazir!" Bhutto's spokeswoman, Sherry Rehman, said the former prime minister was stuck in the house with a handful of top aides. She said Punjab's provincial government had attached the seven-day detention order as well as several padlocks to the front gate. Aftab Cheema, chief of operations of Lahore city police, said Bhutto would not be allowed to leave the house, which was declared a "sub-jail." In a move signalling Bhutto's unwillingess to cooperate with Musharraf and his allies, the former prime minister said once she was freed from detention, she would work to forge a broad alliance, including with Sharif - a longtime rival but one who shares her wish to end military rule. Sharif was ousted by Musharraf in the 1999 coup that brought the general to power. He attempted to return to Pakistan in September but was immediately deported. "Once I'm out, I intend to build a broadbased alliance with a one-point agenda for the restoration of democracy and the rule of law," Bhutto told reporters. "I will be working with all political leaders, including Nawaz Sharif ... We may work side-by-side. The issue is that we both believe there should be democracy." Bhutto said she saw no prospect of achieving political power by cooperating with Musharraf's administration. "Now we've come to the conclusion that even if we get power, it will just be a show of power. It won't be substantive power," Bhutto said. "It seems unlikely that the People's Party will participate in the upcoming elections." She described the vote as a "stage-managed show" to return the ruling party to power. Other Bhutto supporters went ahead with the procession without her. Shah Mahmood Qureshi, president of Bhutto's party for Punjab, said he was leading a column of 200 vehicles from Lahore but they had been stopped by police about 90 kilometers (55 miles) from the city and hundreds of people were detained. There was no immediate confirmation from officials of the arrests. Police initially said they ramped up security around Bhutto due to intelligence that a suicide bomber was planning to attack her in Lahore. Bhutto was targeted by an Oct. 18 suicide attack on a homecoming procession in the southern city of Karachi as she returned from years in exile. She was unscathed, but the blast killed 145 others. She was put under house arrest in Islamabad Friday to prevent her from addressing a rally in the nearby city of Rawalpindi, where authorities issued similar warnings. With Musharraf losing popularity due to growing disaffection with military rule, US officials encouraged him to reconcile with Bhutto in hope of keeping a US-friendly administration in control of the nuclear-armed nation where militants are orchestrating attacks inside the country and across the border in Afghanistan. Extinguishing that prospect puts further strain on Musharraf's relations with Washington, which is pressing him loudly to lift the emergency to ensure that elections are fair. It also wants him to quit his army post. Musharraf, who took power in a 1999 coup and became a key US ally in fighting al-Qaida and Taliban, has set no time limit for the emergency which has also resulted in a ban on rallies and the blacking out of independent TV networks. He signaled Sunday that he wanted to hold the elections with the restrictions in place, raising major doubts over whether the vote could be credible. The emergency came shortly before the Supreme Court was due to rule on the legality of Musharraf's recent re-election for a new presidential term, and critics say it was a tactic to oust independent-minded judges and prolong his eight-year rule.