Lawyers for five alleged al-Qaeda terrorists accused of planning the Sept. 11, 2001, attacks have been subject to “real-time monitoring” of their Internet activities by government officials, a military court here heard Wednesday.

The complaints raise fresh concerns about a justice system previously hit by revelations that an eavesdropping system was hidden in a fake smoke detector in a room where attorneys met their clients and that defense e-mails were turned over to the prosecution.

A military tribunal here also heard that extensive computer problems, which have previously delayed proceedings, have worsened, with files vanishing and e-mails failing to arrive.

Defense lawyers have been ordered by the chief defense counsel in the military commissions system to stop using Defense Department systems for confidential files when working in government offices in Rosslyn. Instead, they have been forced to rely on a nearby Starbucks and hotel lobbies to communicate with colleagues.

They are asking the military judge, Army Col. James Pohl, to delay pretrial proceedings in the death penalty case of the five alleged conspirators until technical problems can be fixed.

David Nevin, lead counsel for Khalid Sheik Mohammed, the self-described mastermind of the attacks on the World Trade Center and the Pentagon, described it as “a motion to abate until we have the fundamental tools to practice law in the 21st century.”

Giving evidence, Col. Karen Mayberry, the chief military defense counsel, said information technology problems had created “an extremely difficult work environment,” adding that “it has become a cumbersome process to complete even the most simple of tasks.”

Nevin questioned Mayberry about three instances of what he described as “real-time monitoring” of his staff’s Internet activity. He said that on one occasion two members of his defense team had been called by government officials with questions about the Web sites they were visiting while using military computers.

Mayberry acknowledged that they had been visiting terrorism-related Web sites as a legitimate part of their duties.

She said that Defense Department systems are monitored “to guard against intrusions, hackers, malwares” and that suspicious activity is flagged to “information security employees of the United States government,” but added that she was seeking changes to protect privileged information.

Mayberry also said that Mohammed’s lawyers discovered that defense documents had been altered by a third party and hidden files had been added to the folder where they were being stored.

Nevin noted that U.S. intelligence services “have an extreme interest in information in relation to the men who are the accused in this case.”

It has previously emerged that privileged defense e-mails had been inadvertently passed to the prosecution, while seven gigabytes of attorneys’ files stored on Defense Department computers have disappeared. Prosecutors said the content of the e-mails was not read.

The problems began in January when IT technicians sought to create a mirror of defense files that could be accessed at Guantanamo.

In April, those concerns prompted Mayberry to order attorneys to stop using Defense Department e-mail accounts and computer networks to save or transmit privileged or confidential information.