ISLAMABAD (Reuters) - Pakistan President Pervez Musharraf imposed a state of emergency in a bid to end an eight-month crisis over his rule fuelled by challenges from a hostile judiciary, Islamist militants and political rivals.

General Musharraf said he decided to act on Saturday in response to a rise in extremism and what he called the paralysis of government by judicial interference.

“I fear that if timely action is not taken, then God forbid there is a threat to Pakistan’s sovereignty,” he said in a midnight televised address, after purging the Supreme Court and rounding up lawyers opposed to him.

“I cannot allow this country to commit suicide.”

There had been increasing speculation that Musharraf, who seized power in a 1999 coup, might declare an emergency rather than run the risk the Supreme Court would rule against his re-election as president last month.

The United States, a staunch Musharraf ally, called the measure “very disappointing”. Musharraf’s announcement effectively dashed U.S. hopes that parliamentary elections due in January would mark a transition to civilian-led democracy.

In the capital Islamabad, armored personnel carriers and military trucks patrolled the streets while roadblocks with metal barriers were set up on the main thoroughfares.

Nuclear-armed Pakistan’s internal security has deteriorated sharply in recent months with a wave of suicide attacks, including an assassination attempt on former Prime Minister Benazir Bhutto last month that killed 139 people.

Bhutto flew back to Pakistan on Saturday from a brief visit to Dubai and accused Musharraf of imposing “mini-martial law” Another leading opposition figure, former cricket captain Imran Khan, was placed under house arrest.

Supreme Court Chief Justice Iftikhar Chaudhry, whose earlier suspension in March marked the beginning of a slide in Musharraf’s popularity, was sacked, Information Minister Mohammad Ali Durrani said.

The court had said on Friday it would reconvene on Monday and decide quickly on whether Musharraf could remain president.

Chaudhry was escorted home by police from the Supreme Court where he and other judges had refused to endorse the emergency.

AL QAEDA

The United States, which regards Musharraf as a crucial ally against al Qaeda in Pakistan and neighboring Afghanistan, had earlier urged Musharraf to avoid taking authoritarian measures.

“This action is very disappointing,” White House National Security Council spokesman Gordon Johndroe said. “President Musharraf needs to stand by his pledges to have free and fair elections in January and step down as chief of army staff before retaking the presidential oath of office.”

But Pentagon Press Secretary Geoff Morrell told reporters the emergency had no immediate impact on U.S. military cooperation. “At this point the declaration does not impact our military support of Pakistan’s efforts in the war on terror.”

Musharraf, who also suspended the constitution, banned the media from publishing anything that defames, ridicules or brings himself, the armed forces or government into disrepute.

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Pakistan Television said that the cabinet, national and provincial assemblies would continue to function and that Abdul Hameed Dogar had been appointed as new Chief Justice.

Witnesses said troops were also deployed at Pakistan Television and radio stations. Most phone lines were down, and private television channels taken off the air.

Musharraf had been awaiting a Supreme Court ruling on whether he was eligible to run for re-election last month while still army chief. He had promised to quit as army chief if he was given a second term.

Farzana Shaikh, a Pakistan expert at London’s Chatham House think tank, said the declaration of emergency by Musharraf was “clearly a pre-emptive move on his part” that was designed to act before the Supreme Court issued its ruling.

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ELECTIONS DELAY

Musharraf’s troubles began in March when he suspended Chaudhry on allegations of misconduct.

Then in July, Musharraf ordered troops to storm the Red Mosque in Islamabad to crush a Taliban-style movement based there. At least 105 people were killed in the raid and a wave of deadly militant attacks and suicide bombings followed.

Musharraf also faced a strong political challenge from Bhutto, who returned to Karachi in October from eight years of self-imposed exile, a homecoming marred by the suicide bombing that killed 139.

On Saturday she went straight from Karachi’s airport terminal to her bullet-proof Landcruiser smiling and waving to hundreds of supporters who chanted: “Long live Bhutto”.

Before the emergency, there had been speculation she would strike a deal with Musharraf to share power after the elections -- an alliance that had been encouraged by the United States.

She said she believed emergency rule was designed to delay elections by “at least one to two years”.

Britain said it was “gravely concerned” by the declaration of emergency rule while India urged a return to democracy.