Members of Yemen's Houthi rebel movement shot dead a young man in the street in Sanaa on Sunday because he refused to fight for them, the victim's father said.
Nabil Fadhel posted an account of the murder of his son, Waleed, 25, on Facebook, saying he was then contacted by phone and asked to send his other son to join the rebels.
Abed Al Hatif, a human rights activist from Sanaa, told The National that Waleed was killed by members of the so-called "popular committees" of the Iran-backed rebels.
Mr Al Hatif said Mr Fadhel told him in a phone call on Monday that Houthi gunmen chased Waleed in a car as he was walking in the street and crashed into him, before getting out and shooting him dead.
"They killed my son because he refused to go to fight with their militia in Hodeidah," Mr Al Hatif quoted Mr Fadhel as saying.
Yemeni forces and the Saudi-led coalition supporting the internationally recognised government launched an operation to retake the port city of Hodeidah last week.
Two rebel fighters captured during the offensive have described how they and others were being forced to fight by the Houthis, who would be considerably weakened by the loss of Hodeidah port.
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Mr Al Hatif said the rebels took Waleed's body to Al Kuwait hospital in Sanaa and were refusing to hand it over to his family.
Mr Fadhel, who heads the Yemen Organisation for Combating Human Trafficking, also posted an appeal to the Houthi interior minister on Facebook, naming three men he accused of killing his son.
News of Waleed's killing was widely shared and condemned on social media by activists in Yemen and abroad.
Among those who tweeted about the murder was Nadwa Dawsari, a non-resident senior fellow at the Project on Middle East Democracy who specialises in civil society and conflict in Yemen.