At least one child died in shelling by Yemen’s Iran-backed Houthi rebels in the city of Marib.

Five others were wounded by shrapnel from a shell fired into a densely populated residential area where internally displaced people live, the country’s state-run Saba news agency reported on Saturday.

Two of the wounded children were in critical condition.

The missile also damaged two homes and a bus in the district when it landed near a playground.

“These are acts of terrorism by the [Houthi] militia and aggression against the Yemeni people,” said Mohammed Shaiea, who witnessed the attack.

“Targeting innocent children in their playgrounds, who should be safe in their homes, is a terrorist act by all means in front of the world.

"Where are the human rights organisations or are they covering up [the attack], where they are when the targets are women and children?”

The Yemeni government accuses Houthi militias of committing crimes against civilians and intensifying bombings of residential neighbourhoods and camps for the displaced in Marib.

The rebels have hit populated areas in the region housing over one million internally displaced people with ballistic missiles and explosive drones.

The conflict in Yemen began after the 2015 takeover of the capital, Sanaa, by the Houthi rebels.

A Saudi-led coalition allied with the government has been fighting the rebels since March 2015.

The Houthis launched a major offensive to capture Marib in January this year, in a bid to seize the last government-controlled region in the country’s north.

The International Organisation for Migration said 21,000 households have been displaced since January due to the fighting.

“With front lines, however, remaining active, local populations and IDPs have continued to bear the brunt of hostilities, seeing their homes destroyed, fleeing their communities and displacement sites, and facing uncertainties over their safety,” the IOM said in a March situation update.

“Almost all new IDPs are being displaced for the second or third time.”

The agency gave a warning that more fighting would just compound the dire situation.

“Should fighting escalate even further into Marib city, IOM and partners estimate that 385,000 people will be displaced further.”

It warned of a lack of resources and few agencies on the ground to assist civilians.

The conflict has created the world’s worst humanitarian crisis and pushed thousands of Yemenis to the brink of starvation.