The militias' spokesman told al-Masirah television that missile and drone attacks hit "sensitive targets" in Riyadh, Jizan and Najran, without giving further details. This escalation contradicts a previous statement that the Houthis welcome a ceasefire.

Yemen has been mired in a civil war since late 2014, when Iran-backed Houthis seized control of much of the country's northern area and forced the Saudi-backed government of President Abd-Rabbu Mansour Hadi out of the capital Sanaa.

A Saudi-led military coalition intervened in the conflict in 2015 to support Hadi's internationally-recognized government. More than 10,000 people have been killed in Yemen since the Arab intervention.