It's time for the United States to hold Iran accountable.

A court in Saudi Arabia has sentenced 15 people to death for spying for Iran and handed 15 others prison terms ranging from six months to 25 years.

They were among 32 men - comprising 30 members of the kingdom's Shia Muslim minority, an Iranian national and an Afghan - put on trial in February. Prosecutors accused them of treason, setting up a spy ring, and passing on sensitive data on military zones.

Tensions between Saudi Arabia and Iran have escalated in the past year.

Sunni-ruled Saudi Arabia broke off diplomatic relations with Shia-led Iran in January following the storming of its embassy in Tehran by protesters angered by the execution of the prominent Saudi Shia cleric, Sheikh Nimr al-Nimr.

Saudi officials insisted Nimr was guilty of terrorism offences, but Iran's supreme leader said he had been executed solely for his criticism of the Sunni monarchy.

The regional powers also back opposing sides in the wars in Syria and Yemen.

Amnesty International said the trial of the 32 men was "grossly unfair".

Taha al-Hajji, a lawyer who represented most of the defendants, told the human rights group that his clients were detained between 2013 and 2014 without an arrest warrant and held for almost three months in secret.

Some told the court they were threatened with solitary confinement and that they would be banned from having contact with their families if they did not sign "confession" documents.

After nearly three years in custody without charge or trial, the defendants were brought before the secretive Specialised Criminal Court in Riyadh in February, where they were handed a list of charges that was almost 100 pages long. Some met their lawyers for the first time, Mr Hajji said.

Several of the lawyers subsequently complained that they were not allowed to visit their clients, view evidence, and prepare their defences adequately.

Visit the BBC for more information about the trials.