HEBRON, West Bank - Israeli police said they were investigating accusations that Jewish settlers killed sheep belonging to Palestinians with poison in a bid to drive Palestinians off their land in the West Bank.

A settler spokeswoman denied the Palestinian allegations that Jews deposited wheat pellets laced with a deadly chemical on grazing land near Hebron, killing 20 of their sheep. She accused Palestinians of poisoning the land as a provocation.

It was the latest chapter in a history of bitter conflict between rightist settlers who stake a biblical claim to occupied territory and Palestinians who want it for an independent state.

The Palestinian governor of Hebron, Arif al-Jabari, told Reuters that the poisoning was part of a "systematic attempt" by settlers to clear the land of Palestinians.

"This is an escalation. They should leave our land," he said. "We will not stay silent. It (poison) led to the death of 20 sheep and poisoning of 82 others that are fighting for their lives."

Palestinian Prime Minister Ahmed Qurie told reporters: "This is a very grave issue."

Palestinians and human rights groups have frequently accused settlers of vigilante violence and acts of harassment aimed at driving them off the land, but say investigations are rare.

A spokesman for Israeli police in the occupied territory said they had begun an investigation. Israeli military administration spokesman Shlomo Dror said settlers could be responsible but an investigation was needed to determine that.

"Some people are trying to make the lives of Palestinians worse," Dror said, alluding to ultra-nationalist Jews in the Hebron area of the southern West Bank. "This is a criminal act."

Both Palestinian and Israeli officials said sheep poisoning was unprecedented. "This is the first time we have seen this kind of act with poison," said Dror.

"We have seen in the past violence against property, like cutting trees and destroying houses and cars, or sometimes even violence against people ... This is very bad," he said, alluding to settler attacks on nearby Palestinian inhabitants.

Settlers have often been the target of suicide bombings and shooting attacks since a Palestinian uprising began in 2000. A ceasefire has been generally holding since February.

Settler spokeswoman Emily Amrusy accused Palestinians of spreading the poison as a provocation. She said settlers had also filed a complaint with police, although no animals belonging to settlers had fallen sick or died.

"We are quite sure that these acts are not from the Jewish people but from the Palestinians," she said.

Ramzi Sansur, a Palestinian toxicologist who examined the pellets in a Bir Zeit university laboratory, said the chemical, Fluoroacetamide, was "extremely toxic" and ordinarily used to kill rodents in sewers.

Palestinian shepherds whose sheep graze in the area told Reuters they saw settlers from a distance appearing to throw substances into the fields in late March.

Days later, their sheep began to fall sick, they said. Some had convulsions and died while others appeared drowsy and had difficulty walking. Other animals including gazelles and migratory birds also died, the Palestinian toxicologist said.