(AFP) - Military prosecutor Lieutenant Colonel Innocent Radjabu on Tuesday urged judges to sentence to death all those on trial, barring one defendant.
The trial began on 7 June in Ndolo military prison, where all the defendants are being held.
The charges include "attack, terrorism, illegal possession of weapons and munitions of war, attempted assassination, criminal association, murder (and) financing of terrorism", according to a court document.
Armed men attacked the home of Economy Minister Vital Kamerhe – who was elected head of the National Assembly three days later – in the early hours of 19 May.
The group then went to the Palais de la Nation that houses President Felix Tshisekedi's offices, brandishing flags of Zaire, the country's name under ex-dictator Mobutu Sese Seko, who was overthrown in 1997.
Shots were heard near the building, several sources said at the time.
An army spokesman later announced on national TV that defence and security forces had stopped "an attempted coup d'etat".
The alleged plot was led by Christian Malanga, a Congolese man who was a "naturalised American" and who was killed by security forces, army spokesman General Sylvain Ekenge has said.
During questioning, the defendants arrested near the Palais de la Nation blamed Malanga. Others detained elsewhere in the capital Kinshasa, including four women, have denied any involvement.
Severe punishment
Richard Bondo, a defence lawyer for one of the American defendants, told the French news agency AFP that the prosecutors' call for the death penalty was "very severe".
The three Americans on trial at the Kinshasa military court include Malanga's son Marcel Malanga.
Tyler Thompson, another of the American defendants, told the trial last month that he had been "forced" into it, echoing the two other US citizens facing the same charge.
"I came to the DRC (Democratic Republic of Congo) to visit Marcel's family who I had never seen before," he added.
Malanga also told the court that he had been forced into participating by his father, saying: "He told us he would kill us if we didn't listen."
Malanga said his father had woken him up late on the night of 18 May, ordering him to take a weapon.
The third American who is being tried – Benjamin Zalman-Polun – also said he was "kidnapped" and "forced" into taking part.
Lawyers for the Americans have complained that their clients were interrogated in French, without an interpreter, despite being English speakers.
The defendants also include a Belgian, a Briton and a Canadian who are all naturalised Congolese.
The defence is due to present its case on Friday.
In March, the Congolese government defied criticism from human rights organisations and lifted a moratorium on the death penalty in place since 2003.
In a separate case earlier this month, a military court in DRC handed death sentences to all 26 defendants accused of belonging to the M23 rebel group after a high-profile trial.