ISLAMABAD, Pakistan (CNN) -- Pakistani security forces clashed Wednesday with supporters of former Prime Minister Benazir Bhutto, who vowed to go forward with a mass rally planned for Friday despite an emergency decree barring such gatherings.
Bhutto has warned that supporters plan to march from Lahore to Islamabad next week
Bhutto called on fellow opposition leaders and the people of Pakistan to join protests against President Pervez Musharraf's state of emergency order. She said 400 members of her political party were arrested across Pakistan on Wednesday "without any provocation."
"Pakistan's unity is under attack," Bhutto told supporters at a news conference outside the parliament building. "The political process is under attack, political leaders are being bombed. ... Our country is in danger from the extremism that has spread under dictatorship."
Shortly after she spoke, Pakistani security forces surrounded the hundreds of demonstrators and fired tear gas canisters into the air, but police sources told CNN there were no arrests.
Uniformed Pakistani police, some in riot gear, and Bhutto's supporters faced off over a spiral of razor wire. Some of the demonstrators clapped and chanted slogans, while others raised Bhutto posters into the air.
Journalists aimed their cameras toward the line of police, who protected themselves with their shields as several protesters pushed the razor wire toward them.
Thousands of lawyers, opposition figures, journalists and human rights workers have been rounded up since Musharraf's emergency decree suspended the constitution on Saturday. Several nations, including Britain, the United States and France, have urged Musharraf to rescind his order, restore the constitution, guarantee elections early next year and step down from his post as army chief of staff.
But Chaudhary Shujaat Hussain, president of the pro-Musharraf Pakistan Muslim League, said Wednesday that elections would be held on schedule. He accused Bhutto of working against democracy and national reconciliation since her return from exile last month, the state-run Associated Press of Pakistan reported.
Pakistan's parliament -- which handed Musharraf an overwhelming presidential election victory in October -- voted Wednesday to approve the emergency order. But many opposition legislators were not in attendance, a fact that did not escape Prime Minister Shaukat Aziz.
"They should participate in the proceeding of the Assembly and express their point of view," Aziz told the National Assembly, the APP reported.
"The opposition should come at a common platform on the national issues as it has an important role to play," he said. "There is a need to create a peaceful atmosphere as the general elections are approaching."
Musharraf has insisted the declaration was necessary to the country's fight against terrorism and will not derail its slow progress toward democracy. But opposition leaders accuse him of moving to shut down the judiciary just before the Supreme Court was to nullify the parliamentary vote that gave him a third term.
At her news conference, Bhutto said her Pakistan People's Party will be going ahead with a peaceful rally Wednesday night and Bhutto will attend a larger rally on Friday in Rawalpindi -- the city outside Islamabad where Pakistan's military, led by Musharraf, is based. She urged all opposition parties to put aside their differences and join the rallies.
But Punjab provincial authorities have said they will bar Friday's demonstration because it is outlawed under the emergency measures.
Asked if she had fears about security in Rawalpindi, Bhutto said she is "concerned," but stressed that she believes there are "much greater stakes here that we are talking about."
"We are talking about the impact on the region if a nuclear-armed country like Pakistan explodes," she said.
Bhutto already has survived a massive suicide bomb attack in October that killed more than 130 people. The blast ripped into spectators who turned out to watch her motorcade in Karachi the day she returned from exile.
She reiterated her demands that Musharraf restore the constitution, stand by his pledge to retire as army chief by Nov. 15 -- when he is set to take the oath of office as president -- and set parliamentary elections on that day to take place by January 16.
If her demands are not met, she said, she will organize a march from Lahore to Islamabad next Tuesday.
The United States, Britain and other countries have urged Musharraf to lift the emergency declaration and return to a constitutional government by setting a date for elections. President Bush said that he delivered that message personally to Musharraf during a Wednesday phone call.
"My message was very plain, very easy to understand, and that is, the United States wants you to have the elections as scheduled and take your uniform off," Bush said during an appearance with French President Nicolas Sarkozy at Mount Vernon, the Virginia home of the first president of the United States, George Washington.
While the United States and Britain have said they are reviewing current aid packages with an eye toward possible withdrawal, only the Netherlands has cut off financial aid to Pakistan.
John Negroponte, the former director of National Intelligence who now serves as deputy secretary of state, told the House Foreign Affairs Committee Wednesday that U.S. officials "strongly disagree" with Musharraf's actions, but "that disagreement should not translate into disengagement."
Negroponte said Bush considers Musharraf to have been "an indispensable ally in the global war on terrorism." He credited the general with having strengthened Pakistan's human rights, civil society and news media groups and having made Pakistan "a more moderate and prosperous country."
"Pakistan's future is too vital to our interests and our national security to ignore or to downgrade," he said. "Our challenge is to deal with the government in a way that supports the Pakistani people and helps them strengthen the influence of the moderate center in its fight against violent extremism." E-mail to a friend
CNN's Mohsin Naqvi in Lahore contributed to this report