Tens of thousands of people protested in Houthi-controlled parts of Yemen on Monday, the Iran-backed rebels' Al-Masirah TV showed, two days after US attacks that left dozens dead.

Demonstrators waved placards and assault rifles, chanting "Death to America, death to Israel", at a huge protest in the capital Sanaa, while rallies were also held in Saada, Dhamar, Hodeida and Amran.

The demonstrations were called by the rebel group's leader Abdulmalik al-Huthi.

In the capital, seized by the Houthis in 2014, giant Yemeni and Palestinian flags punctuated a sea of demonstrators at Al-Sabeen Square, the site of weekly protests throughout the Gaza war.

"Yemen will never back down -- we defy the Americans, we defy the Zionists," said a man shouting slogans to the crowd.

Fifty-three people died and 98 were wounded in Saturday's US attacks on Sanaa and other areas, according to the Houthi health ministry.

President Donald Trump ordered the attacks following months of Houthi attacks on the vital Red Sea maritime trade route, despite a pause since Gaza's ceasefire started in January.

In retaliation, the rebels claimed to have twice attacked a US aircraft carrier group within 24 hours.

The Huthis, part of Iran's "axis of resistance" against the US and Israel, launched scores of drone and missile attacks on passing ships and Israeli territory during the Gaza war, claiming solidarity with the Palestinians. (AFP)