They urged the court to annul evidence from earlier hearings involving their clients, alleging irregularities such as the absence of interpreters.

The alleged coup bid struck on May 19 when armed men attacked the home of Economy Minister Vital Kamerhe before raiding the building housing the offices of President Felix Tshisekedi.

US nationals Marcel Malanga and Taylor Christian Thomson, both 21, and 36-year-old Benjamin Reuben Zalman-Polun are among 51 people accused by the Congolese military of participating in the coup.

Their lawyers said minutes from the hearings were drawn up without the assistance of interpreters -- even though the defendants speak English and the hearings were conducted in French.

Thomson's defence said that he had lodged a civil claim in the case, denouncing acts of "inhuman and degrading treatment" during his arrest, referring to videos of the defendant stripped naked that were widely circulated on social media.

Lawyers for Jean-Jacques Wondo, a Congolese-Belgian, requested "provisional release on health grounds".

Wondo is "diabetic and hypertensive", but since his arrest he has been forbidden to take his medication, "which is suicidal", said lawyer Peter Ngomo.

The trial began on June 7 in Ndolo military prison where all the defendants are being held.

In the first hearing, Judge Freddy Ehume told the court that the actions of the three Americans were "punishable by death".

The next hearing will take place on Tuesday.