Western diplomats working with the Palestinians have received letters warning them that they are "at risk" because of their nations' criticism of settlements, sources told AFP on Thursday.
Sources at several foreign missions in east Jerusalem said a group of men who appeared to be Israeli settlers had handed threatening letters to diplomats as they went through a military checkpoint by the West Bank city of Ramallah.
The unsigned letter, a copy of which was obtained by AFP, warns diplomats to "Go home!"
"You are guests in our country! You are standing on the Holy Land of the Jewish nation. Do not interfere with the building of our country," the letter says.
"The meddling by the American government and by the European Union is putting your stay at risk... We never will make peace with Palestinian terrorists!" the letter warns.
The one-page letter printed in capital letters is accompanied by a second sheet of paper printed with the words "President Barack Hussein Obama - with friends like you who needs enemies!!!"
An official at the US consulate in east Jerusalem, who spoke on condition of anonymity, said the mission's employees had received the letter last week.
"The US consulate can confirm that it has been a recipient," he said, adding that no specific additional security measures were being prepared.
"We have precautions in place already, but there's nothing new," he said. "We would defer to the proper authorities to deal with it."
A spokesman for the Israeli foreign ministry could not immediately be reached.
Other diplomatic missions in east Jerusalem said the letter was being discussed.
"Internally we are aware of this and we are looking into it," EU mission spokeswoman Antonia Zafeiri told AFP.
Israeli settlement building in the West Bank and east Jerusalem is among the most contentious issues in the Israeli-Palestinian conflict.
Last year, direct peace talks ground to a halt shortly after they started when a 10-month partial Israeli settlement freeze expired and Israeli Prime Minister Benjamin Netanyahu refused to renew it.
The Palestinians have said they will not hold peace talks while Israel builds on land they want for their future state.
The international community considers Israeli settlements built on occupied land in the West Bank and east Jerusalem as illegal, and 14 of the 15 members of the United Nations Security Council last month backed a resolution condemning the Jewish state for continuing settlement activity.
The United States vetoed the resolution, saying it did not think the United Nations was the appropriate forum to address the issue, but reiterating its opposition to Israeli settlement building.