Sana’a: Shiite Al Houthi rebels backed by tanks launched a fresh attack on Friday on a town in north Yemen held by their Sunni Salafist rivals, a Salafist spokesman said, bringing the total death toll in three days of sectarian clashes to 40.

The fighting erupted on Wednesday despite government mediation efforts to shore up a ceasefire in place since late last year in the mountainous Sa’ada province, which has long been outside the control of the central Yemeni authorities.

Salafist spokesman Abu Esmail Al Hajouri told Reuters the casualties were all Salafists and that at least 200 more people had been wounded during the Al Houthi offensive against the town of Damaj.

Damaj lies near Sa’ada, a Al Houthi-controlled city near the Saudi border 130km north of the capital Sana’a.

Sa’ada province is the base for a long-running Houthi rebellion against the Yemeni government. Saudi Arabia’s military intervened in 2009 before a ceasefire took hold the year after.

The province has since fallen openly into Al Houthi hands with a Al Houthi-imposed governor.

Hajouri said Damaj had been besieged by Al Houthi rebels for weeks and accused them of shelling the city with rockets that set on fire dormitories for students at a religious school.

Meanwhile, the Red Cross called for an “immediate” ceasefire in deadly clashes between Zaidi Shiite rebels and Sunni Islamists to allow the wounded to be evacuated.

“The ongoing clashes have been preventing us reaching people who urgently need our help,” said Cedric Schweizer, the International Committee of the Red Cross delegation head in Sana’a.

“Every minute we lose waiting to get into Dammaj and the surrounding area is a potential life lost,” he warned in a statement.

“We are calling for an immediate and solid ceasefire, which would allow our colleagues to evacuate the wounded and deliver life-saving care.”

The Zaidis, also known as Al Huthis after their late leader Abdul Malek Al Houthi, rose up in 2004 against the government of ex-president Ali Abdullah Saleh, accusing it of marginalising them politically and economically.

Thousands of people were killed in the uprising before a ceasefire was agreed in February 2010.