Food remnants were left on the tombstones
Damaged graves and racist graffiti have been found in the Palestinian village of Awarta in the northern West Bank after a Jewish group visited the area.
Palestinians said they had seen Jewish pilgrims, escorted by Israeli soldiers, in the area, which is also a Jewish burial site.
The Israeli military said it viewed the incident very seriously and was opening a military police investigation.
It comes a month after an arson attack on a mosque in the same area.
At least two tombstones were damaged in the cemetery outside the village, and food and rubbish were left on graves.
In the village, offensive slogans about Arabs were found scrawled in Hebrew, English and Russian.
Israelis are forbidden from entering Awarta, but the Israeli military occasionally organises group trips for settlers to visit nearby Jewish tombs.
Palestinians told the Israeli rights group B'tselem that such a visit had taken place on Tuesday night, and the damage was discovered on Wednesday morning.
B'tselem said the tombs may have been ones that had been previously broken and repaired.
Local media quoted a group that organises visits by settlers to Jewish tombs as saying "we have no right wing or anti-Arab ideology and if someone from our group is found responsible for these acts, we would be the first to condemn them".
This comes two days after 10 Jewish settlers from the nearby settlement of Yitzhar were arrested in a pre-dawn raid.
Police said they wanted to see if there was a link between the individuals and the burning of a mosque in the village of Yasuf in December.
Offensive slogans were daubed on the mosque wall in Hebrew.
Some hard-line settlers have said they will attack Palestinians in retaliation for any Israeli government measures they see as threatening Jewish settlements.
The Israeli Prime Minister Benjamin Netanyahu recently announced a ten-month lull in permits for new settlement homes on the West Bank, not including East Jerusalem.
All Jewish settlements in the West Bank, occupied by Israel in 1967, are illegal under international law, although Israel disputes this.