A bomb explosion on Wednesday in an open market in Yemen's oasis city of Marib killed seven people and wounded 18, security and medical sources said.

The blast targeted a market selling qat, the mild narcotic leaf popular in the Arabian Peninsula country, a security official in Marib said.

A medical source at the city's public hospital confirmed the toll.

Forces loyal to President Abedrabbo Mansour Hadi control Marib, which is east of Yemen's rebel-held capital Sanaa.

The province of Marib has seen fierce battles between Hadi loyalists and Shia Huothi rebels and their allies, who continue to control northern parts of the governorate.

A Saudi-led coalition which intervened in March last year against the Iran-backed rebels has forces based in Marib province to support the loyalists.

More than 6,400 Yemenis, most of them civilians, have been killed since last March, and the fighting has driven 2.8 million people from their homes.