A military court in the Democratic Republic of the Congo (DRC) has sentenced to death 37 people, including three United States citizens, on charges of taking part in a failed coup in May.

“The court pronounces the harshest sentence: the death penalty for criminal association, the death penalty for attack, the death penalty for terrorism,” the court’s president, Freddy Ehume, said in a verdict read on live television on Friday.

The defendants – who also included a Briton, Belgian and Canadian – have five days to appeal the verdict. Fourteen people were acquitted in the trial, which opened in June.

Richard Bondo, the lawyer who defended the six foreigners, told The Associated Press news agency he disputed whether the death penalty could currently be imposed in the DRC despite its reinstatement this year and said his clients had inadequate interpreters during the investigation of the case.

“We will challenge this decision on appeal,” Bondo said.

At the time of the attempted coup, military officials said armed men had briefly occupied an office of the presidency in the capital, Kinshasa, on May 19. Their leader, US-based Congolese politician Christian Malanga, was killed by security forces, and two security guards were also killed in the failed takeover.

Malanga, who styled himself “President of New Zaire”, was a wealthy businessman, politician and one-time military captain in the Congolese army. He contested parliamentary elections in 2011 but was arrested and detained for several weeks under former President Joseph Kabila.

Upon his release, Malanga went to the US, where he founded the opposition United Congolese Party (UCP). Over the years, he campaigned for religious freedom in Africa and led anticorruption training initiatives for young Africans in Europe.

President Felix Tshisekedi was sworn in for a second term in January after elections that were marred by logistical issues, irregularities and violence.

Western and Central Africa have experienced a series of coups over the past few years.

Human Rights Watch had called on Congolese authorities to ensure the trial met international standards. “Congo and the region have a legacy of coups and attempted coups,” Lewis Mudge, Central Africa director at Human Rights Watch, said shortly after the failed coup. “The Congolese government needs to treat this crisis as an opportunity to demonstrate its commitment to human rights and the rule of law.”

Malanga’s son, Marcel Malanga, was sentenced to death on Friday along with Taylor Thompson, who played high school football with him in Utah, and Benjamin Zalman-Polun, a business associate of the late elder Malanga.

Marcel Malanga had previously told the court that his father had threatened to kill him unless he participated. He also told the court it was his first time visiting the DRC at the invitation of his father, whom he hadn’t seen in years.

Another defendant sentenced on Friday is a Belgian military expert.

“A majority of them, they came from the diaspora,” Al Jazeera’s Alain Uaykani said, reporting from Goma in the eastern DRC. “This coup was not organised by the military of the country or police officers here in the country.”

The DRC lifted a moratorium on the death penalty in March, citing treachery and espionage in recurring armed conflicts as the reason.