TRIPOLI — (CNN) A Tripoli court sentenced several officials in the former regime of slain Libyan leader Moammar Gadhafi to death Tuesday — including Gadhafi’s son Saif al-Islam Gadhafi in absentia — drawing criticism from the U.N. human rights office.

Saif al-Islam Gadhafi was ordered to face a firing squad for his role in trying to quash the 2011 revolution that led to his father’s ouster.

Several other Gadhafi regime officials were also sentenced to death, including former Libyan spy chief Abdullah al-Senussi, former Prime Minister Al-Mahmoudi al-Baghdadi and former foreign intelligence chief Buzeid Dorda.

Saif al-Islam Gadhafi was not at the trial, as he is being held by a militia group in the northwestern city of Zintan. He has been held there since his capture in November 2011.

Gadhafi faced charges relating to the 2011 revolution and attempts to suppress the uprising, including the killing of protesters — a crime punishable by death.

But it’s not clear what happens to him now, as the Zintan militia holding him doesn’t recognize the government and court in Tripoli.

The militia has also cut off cooperation with the proceedings.

The office of the U.N. High Commissioner for Human Rights said Friday it was “deeply disturbed” by the verdicts and sentences, asserting that the trial failed to meet international standards for fair trials.

“Among the key shortcomings are the failure to establish individual criminal responsibility in relation to specific crimes,” the U.N. office said.

“There were also serious issues relating to access to lawyers, claims of ill-treatment, and trials conducted in absentia.

“It is crucial to ensure accountability for serious human rights violations. However this needs to be done with scrupulous adherence to international fair trial standards and with full respect for the rights of the defendants. Failing this, injustice is only compounded.”

The office urged Libya to pass legal reforms and ensure that the verdicts could be appealed.

Gadhafi was once considered the heir apparent to his father, who ruled Libya for over 30 years.

Before the 2011 Libyan civil war, he was believed to be a moderate in comparison to his father.

A NATO strike in May 2011 killed his younger brother who had a similar name, Saif al-Arab Gadhafi.

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