"This horrific massacre is within a series of systematic killings of civilians by the terrorist Huthi militia," he wrote in English.
The Huthis have yet to comment on the attack, which comes as fighting between the Iran-backed rebels and government forces supported by a Saudi-led military coalition intensifies.
On Thursday children were among 13 people killed when a missile fired by the rebels struck a tribal leader's home in Al-Jawba, according to military and medical officials.
Marib, capital of the oil-rich province of the same name, is the internationally recognised government's last bastion in northern Yemen.
The Huthis began a major push to seize the city in February and, after a lull, they have renewed their offensive in recent weeks. They claimed this week to have reached the vicinity of Marib city and to have nearly surrounded it.
The Saudi-led coalition has been conducting an aerial bombing campaign since 11 October to prevent the rebels from reaching Marib city. Since then, more than 2,200 Huthi fighters have been killed in Al-Jawba and two other districts, according to the coalition.
The rebels rarely comment on losses, and AFP could not independently verify the toll. Yemen's civil war began in 2014 when the Huthis seized Sanaa, prompting Saudi-led forces to intervene to prop up the government the following year.
Tens of thousands of people have died and millions have been displaced in what the United Nations calls the world's worst humanitarian crisis.