· Ex-cricketer held after coming out of hiding · President says he may step down as army chief soon

Imran Khan, the cricketer turned opposition firebrand, was imprisoned yesterday under Pakistan's draconian anti-terror laws, silencing another prominent critic as the emergency rule crisis deepened.

His arrest came as the military ruler, General Pervez Musharraf, defended the crackdown, in which at least 5,000 people have been detained, saying he expected to step down as army chief by the end of November.

But Musharraf's western allies want him to rescind the authoritarian rule imposed 12 days ago as quickly as possible. Washington dispatched the deputy secretary of state, John Negroponte, who is due in Islamabad tomorrow, to drive home its case.

"I am not a dictator, I want a democracy," Musharraf told Sky News in one of several interviews, by turn defiant and defensive, given in recent days. "The day when there is no turmoil in Pakistan, I will step down."

He told the Associated Press he would resign from the army once a supreme court challenge to his rule as a civilian was decided, probably by the end of the month. "I take decisions in Pakistan's interest and I don't take ultimatums from anyone."

Opposition hopes now lie with Benazir Bhutto, who spent a second day under house arrest in Lahore after authorities thwarted a planned "long march" through Punjab province. Bhutto has called on Musharraf to give up power but has not yet thrown her lot in with other opposition parties.

The ease with which Musharraf has crushed dissent was evident at Punjab University, where Khan emerged yesterday after two weeks in hiding. The former cricket captain, who leads a small opposition party, had been a fugitive since police tried to arrest him shortly after emergency rule was imposed. He has flitted between safe houses, promising in phone interviews to lead a "student revolution".

Amid cheering from a crowd of several hundred people he was hoisted on to supporters' shoulders at Punjab University. But moments later he was dragged into a physics building by activists from the student wing of Jamaat Islami, Pakistan's largest Islamist party. A burly student held Khan in a headlock.

The JI students had warned Khan against bringing his campaign to the university, which has been a stronghold of the often violent Islamist activists since the 1980s. "This is just for his protection. We are gathering students so that the [intelligence] agencies cannot enter the campus," said one bearded student.

An hour later Khan was bundled into a white van and driven to the campus gates, where police took him into custody.

He was charged under the anti-terrorist act, most often used against political opponents of the Musharraf regime. Penalties under the act include life imprisonment and death, although police did not specify the charges against Khan. He was being held at an undisclosed location.

"I want the students to be mobilised, as well as the lawyers and the political parties, because it has to be a comprehensive movement against the brute force of a military dictator," he said shortly before being taken away.

The chaotic scenes underscore the difficulties facing Pakistan's fractious opposition. Speaking from exile in Saudi Arabia, the former prime minister Nawaz Sharif offered to bury differences with Bhutto to forge a united front.

Officials said Bhutto could be released from house arrest as early as today. Khan is unlikely to get out so quickly. Before emergency rule he regularly featured on TV chat shows, denouncing Musharraf.

Since emergency rule critical TV stations have been blacked out and political rallies banned. But Musharraf insists that free and fair elections are possible by January 9. "Emergency is not meant to rig elections. Emergency is in fact meant to make sure that elections are held in a peaceful manner," he said.

Pro-Taliban militants continued a march across troubled North-West Frontier province. Two days ago Islamist fighters captured a town in Swat, a tourist area near the Afghan border. Yesterday the army said it had killed 16 fighters in three separate incidents.