Three followers of the Baha'i faith in Yemen have reportedly been sentenced to death by a court controlled by the rebel Houthi movement.
The Baha'i community in the UK said the unnamed individuals had been convicted of espionage and apostasy.
They were being tried alongside 21 other people by a judge who sentenced a Baha'i man to death last January.
Baha'i representative Diane Alai said they had been "falsely and maliciously accused under absurd pretexts".
She urged the international community to "condemn these baseless actions in the strongest possible terms and call for the immediate release of all detained Baha'is".
In a speech in March, rebel leader Abdul Malik al-Houthi denounced the Baha'i faith as "satanic" and claimed it was "waging a war of doctrine" against Islam.
The Baha'i faith was founded in Iran in the mid-19th Century by Mirza Husayn Ali, a man known as "Baha'ullah" ("Glory of God").
Baha'is believe that all the founders of the world's major religions have been manifestations of God and agents of a progressive divine plan for the education of humanity, and that Baha'ullah is the most recent manifestation of God.
Today, there are an estimated five million Baha'is worldwide. There are only a few thousand in Yemen, where 99% of the 27 million population is Muslim.
The Houthi movement has cracked down on Baha'is since its supporters drove the Western-backed government of President Abdrabbuh Mansour Hadi out of the capital Sanaa and seized control of much of western Yemen in 2015.
The UN has said Bahai's living in rebel territory have faced a "persistent pattern of persecution", including harassment and arbitrary detention.
In January, UN human rights experts urged the Houthi-led authorities to annul a death sentence handed down against a Baha'i man, Hamid Kamali bin Haydara, who was accused of "compromising the independence of the Republic of Yemen" and spreading the Baha'i faith in the country.
A number of trials against Mr bin Haydara, including the one during which the death sentence was imposed, took place without him being present, and his lawyer was not given the opportunity to contest the evidence presented against him.
The Baha'i Community of the UK said the judge who convicted Mr bin Haydara had also sentenced to death the three other Bahai's on Saturday.
They were among 24 Bahai's, including eight women and a teenage girl, who went on trial last month on the charges of spying for a foreign state and apostasy.
There was no immediate confirmation from the Houthi authorities, but on Saturday the rebel-run Saba news agency reported that a court in Sanaa had sentenced three men to death for "collaborating with a foreign country".
It said one man was accused of seeking to recruit people to fight for Saudi Arabia, which is leading a coalition of Arab states supporting Yemen's government in its war with the Houthis, and that the other two allegedly provided military information.