An Egyptian court on Monday sent liberal politician and former presidential candidate Ayman Nour to jail until December 10 in the middle of his trial for forgery.
Nour's lawyer, Amir Salim, said the judge's unusual decision looked like the prelude to an early verdict in the trial.
However, Nour's wife and spokeswoman Gameela Ismail said later she doubted the judge would cut off the defence case so early.
Nour was President Hosni Mubarak's main rival in Egypt's first presidential election in September, winning 8 percent of the vote compared with 89 percent for Mubarak.
He was detained for six weeks earlier this year for questioning about the forgery charges but was freed after the United States put public pressure on the government.
Nour, who had been confined to a cage inside the packed courtroom during a session of the trial, was taken to court cells then put in a police truck and driven to Tora prison south of Cairo, where he spent his previous period of detention.
Salim said the judge had ordered him to be detained until December 10. "This is an indication that he is going to give them sentences on that day," Salim told Reuters.
However, Ismail said: "It's strange what the judge did but it would be a serious violation if he closes the case before the defence team finishes. The lawyers for most of the defendants haven't even started yet."
Nour was first detained in January, released in March and then charged with submitting forged signatures when his opposition Ghad Party applied last year for legal recognition.
Ghad Party Secretary-General Wael Nawara said: "Nour has been very co-operative with the court throughout the trial and has been punctual in all court hearings. We do not understand why such a decision has been made."
"This comes as a serious, uncalled-for and unjustifiable development that is quite unbelievable," Nawara said in an e-mailed statement after the decision was announced.
Nour's supporters inside the courtroom started singing the national anthem after the judge announced his decision.
Outside the building, which was surrounded by hundreds of riot police, more than 100 supporters shouted "Down with Mubarak" and "Freedom, where are you? The security forces stand between you and us."
Nour and his supporters have said the forgery charges are fabrications aimed at disrupting Nour's campaign in the presidential race.
In Egypt's staggered legislative elections that began on November 9, Nour lost his parliamentary seat, which he blamed on intimidation, voter fraud and tampering with ballot boxes.
The government has said the elections are free and fair.
A rival Ghad leadership sprang up before the parliamentary elections, seriously disrupting Nour's campaign. Nour's supporters say the rivals are working for the government, a charge which they and the government deny.
Ismail said: "This detention is the last link in a long chain of violence, harassment and intimidation. It's the last part of the show. They want to get rid of him (Nour) so that he can't practise politics ever again."