Gen. Pervez Musharraf sent troops into Pakistan's capital Saturday and suspended the country's constitution. He said he was forced to declare a state of emergency because Islamic extremists were threatening the government's authority.

"With all my conviction, and with all of the facts available to me, I consider that inaction at this moment is suicide for Pakistan," Musharraf said.

But his move has angered many in Pakistan and around the world.

Saturday night, there were reports of aerial gunfire in the city of Karachi. There were also reports that police were rounding up opposition leaders.

Earlier in the day, Musharraf's critics lashed out.

"What you're seeing is the act of a bold, but very desperate man," said Akbar Ahmed, the former Pakistani ambassador to the United Kingdom.

Canada's government also condemned the measures. A statement released by Foreign Affairs Minister Maxime Bernier called on Musharraf to "immediately" cancel the state of emergency and the new provisional constitutional order.

"These measures undermine democratic development, judicial independence and the possibility of free and fair elections to which the people of Pakistan are entitled," said Bernier.

"We urge the government of Pakistan to end emergency rule and call on the government to respect judicial processes and reinstate the judiciary, adhere to the rule of law, and allow free and fair parliamentary elections to proceed as planned."

Musharraf invoked the emergency measures on Saturday -- an action the United States called "very disappointing."

In a televised address to the nation, Musharraf said Pakistan was at a "dangerous" juncture due to the constant threat of Islamic extremists. He added that he hoped democracy could be returned to Pakistan after parliamentary elections.

"In my eyes, I say with sorrow that some elements are creating hurdles in the way of democracy," Musharraf said Saturday. "I think this chaos is being created for personal interests and to harm Pakistan."

The country's Supreme Court was to rule in the coming days on whether Musharraf was legally able to run as a presidential candidate in last month's elections, considering he still heads the army.

Musharraf -- who took power in a 1999 military coup -- presented the top court with the declaration of emergency. Seven judges refused to ratify it and ordered the prime minister and military officers not to comply.

"We feel that government has no ground/reason to take extra constitutional steps, particularly for the reasons being published in the newspapers that a high-profile case is pending and is not likely to be decided in favour of the government," the judges wrote in a two-page ruling.

Musharraf's government suspended the country's constitution. It told Iftikhar Mohammad Chaudhry, Chief Justice of the Supreme Court, that his services were no longer required after the judge refused to take an oath under the provisional constitutional order.

Witnesses say Chaudhry -- whom Musharraf had tried unsuccessfully to oust earlier this year -- and other top judges left the court buildings under police escort.

A new chief justice has been named -- Abdul Hameed Dogar.

Military troops are patrolling the capital of Islamabad and blocking roads. Phone lines are down in Islamabad and transmissions by private TV news channels there and in several other cities have been blocked.

Political, military turmoil

Government troops have been battling militants in the northern district of Swat in recent days. The militants there want Islamic Shariah law imposed -- a move that has local support.

In addition, there have been intense clashes in North and South Waziristan, which sits adjacent to Afghanistan.

The violence has significantly flared since government troops stormed the Red Mosque, an Islamist hotbed in Islamabad, in July. Since then, more than 800 people have died in suicide bombings.

In Istanbul, Turkey, U.S. Secretary of State Condoleezza Rice criticized Musharraf.

"The U.S. has made clear it does not support extra-constitutional measures because those measures take Pakistan away from the path of democracy and civilian rule," she said.

The U.S. sees Musharraf as a key ally in the so-called war on terror.

India, which has fought three wars with Pakistan since 1947, urged a speedy return to "normalcy" and "democracy."

Parliamentary elections are scheduled for January in Pakistan, but it is still unclear how Saturday's development will affect that process.

Benazir Bhutto, a popular opposition leader and former prime minister, ended her eight-year, self-imposed exile and returned to Pakistan last month to take part in those elections after reaching a deal with Musharraf.

"We the political parties are calling for the restoration of the constitution, and for the holding of the elections under an independent election commission," she told the BBC.

The spokesperson for another former prime minister also blasted Musharraf.

"This is the most condemnable act," said Ahsan Iqbal, a spokesperson for the opposition PML-N party of former prime minister Nawaz Sharif. "The whole nation will resist this extra-constitutional measure."

Musharraf barred the exiled Sharif from returning to Pakistan in September to mount a campaign against military rule.

Defence and security analyst Sunil Ram told CTV Newsnet that Musharraf has triggered crises before to keep his grip on power.

"You'll notice that every time a key terrorist/martial law type situation occurs, it is generally right before a political decision is being made on his right to have the duality of being the head of the military as well has the head of the civilian government," he said.

"So this event isn't a surprise."

With files from The Associated Press