JERUSALEM, Oct 8 (Reuters) - Headstones at a Muslim and a Christian cemetery were desecrated by unknown assailants in Jaffa on Saturday, the Jewish holy fast day of Yom Kippur, an Israeli website said.

Pictures on the www.nana10.co.il Hebrew website showed one gravestone with the words death to Arabs spray painted in Hebrew and the words Price tag, a slogan used by militant Jewish West Bank settlers and their supporters, on another.

A third photograph showed a broken tombstone but none of the photographs could be independently verified due to the fast day's traditional travel limitations.

The price-taggers have vowed to avenge any move by Israel to uproot settlement outposts built in the occupied West Bank without Israeli government permission and have torched mosques and vandalised both Israeli and Palestinian property.

Police and Jewish Israeli officials were not available for comment during the Yom Kippur fast day and a local Muslim community leader in Jaffa quoted in the article did not reply when contacted by Reuters.

Jaffa is the ancient part of Tel Aviv which has a mixed Arab and Jewish population.

On Monday, a mosque in a Bedouin village in northern Israel was set on fire and graffiti sprayed on its walls in an attack authorities have blamed on hardline Jewish settlers.

The torching drew broad condemnation from top Israeli leaders and President Shimon Peres and the country's chief rabbis also visited the scene to calm tensions.

In 2005 a Jewish couple was charged for throwing a pig's head into a Tel Aviv mosque in an attempt to derail Israel's then pullout from the Gaza Strip which went ahead in August of that year.

In 2008 riots erupted in the coastal city of Acre in northern Israel when Jews accosted an Arab man who drove his car into a predominantly Jewish neighbourhood during Yom Kippur when all traffic halts and the country shuts down for 24 hours. (Writing by Ori Lewis)