Five civilians were killed and 20 others injured in a Houthi attack in eastern Yemen's Marib city on Tuesday, according to a local police source.

Houthi rebels fired a mortar shell on a crowded street in the city, a police officer told Anadolu Agency on condition of anonymity due to restrictions on speaking to media.

Yemen's official Saba news agency said the shell struck a marketplace in the city.

The source said the death toll was expected to rise as many of the injured were in a serious condition.

Houthis hold a mountainous area in Sirwah district near Marib, from where they launch attacks on civilian and military targets in the city. Marib is about 115 kilometers, or 70 miles, east of the capital, Sanaa.

Impoverished Yemen has been wracked by conflict since 2014, when the Shia Houthi group overran much of the country, including Sanaa.

The conflict escalated in 2015 when Saudi Arabia and its Sunni-Arab allies launched a wide-ranging military campaign aimed at rolling back Houthi gains in Yemen.

Riyadh has repeatedly accused the Houthis of acting as a proxy military force for Shia Iran, Saudi Arabia's arch-foe in the region.

The war has killed more than 10,000 people and displaced more than 3 million, and pushed Yemen's 28 million people to the brink of famine.