Yemen's seven-year brutal civil war has caused mental illness, post-traumatic stress disorder and psychosis, overwhelming the basic health care services.

"We try to provide treatment, but we cannot treat everyone," said Adel Melhi, director of a psychiatric hospital in the rebel-blockaded city of Taez, one of the places hardest hit by the conflict.

Iran-backed Huthi rebels have fought a Saudi-led pro-government coalition since 2015 in a grinding war that has killed hundreds of thousands and pushed the impoverished nation to the brink of famine.

Aid groups have raised the alarm with more than 23 million people – more than two-thirds of Yemen's population – dependent on aid.

While the government-run Taez psychiatric hospital has space for 200 patients, the numbers needing care because of the "tragedies caused by the war" have surged far higher, Melhi said.