At least 20 people were killed and 15 others wounded, when Saudi-led war planes attacked a hospital, operated by the humanitarian association, Doctors Without Borders (MSF) in Yemen's north-west province of Hajja on Monday, a MSF spokeswoman and an eyewitness said.

"It is confirmed that a Saudi-led air strike today hit a hospital run by the MSF team, since July 2015, in Abbs district," MSF spokeswoman, Malak Shahir, said.

She said the doctor team is busy treating the injured.

An eyewitness said that, the air strike destroyed a part of the hospital, but the hospital is still being operated by the MSF doctors.

He said that a Spanish female doctor survived the air strike and she is now treating the injured.

It's not the first time MSF-run hospitals were hit by the Saudi-led war planes.

A few months ago, two MSF-run hospitals in neighbouring Saada province were hit by several air strikes, as the Saudi-led military coalition admitted its mistakes.

On Saturday, another Saudi-led air strike raided a school in Haidan district in Saada province, killing at least 10 students and injuring 28 others, according to an MSF statement.

The Saudi-led war planes, fighting Shiite Houthi rebels, launched air strikes against military targets of Houthis and their ally forces loyal to former President, Ali Abdullah Saleh, in several northern provinces on Monday, including the capital Sanaa, according to reports.

Saudi Arabia and its allies intervened in support of exiled Yemeni government in 2015, but failed to bring it back to power, in the rebel-held capital Sanaa.

The war and air strikes have since killed over 6,400 people, mostly civilians.