At least half a dozen billboards recently went up across the West Bank warning Palestinians of an impending judgment day, slated according to the signs, for May 21.

At the entrance to Birzeit, and several roads leading into the West Bank cities of Ramallah and Jericho, the signs -- some in English, some in Arabic -- advise travelers to "cry unto God" and are directed to the website of the US-based religious group.

Contacted about the purpose of the signs, the Oakland, California-based group Family Radio replied with a statement saying the signs are to inform Palestinians of "the great urgency that now exists for each and every person to be reconciled with God before May 21, 2011."

Similar signs were installed in the Jordanian capital city of Amman, according to a Palestinian student blogger, but were taken down after citizens protested, calling them offensive.

"Only God knows when the judgment day will be," the writer quoted disgruntled Christians as saying in response to the signs, saying himself that the signs were "against the religion of Islam."

According to the Family Radio statement, next Saturday "will be the day when God comes for His people, and also the appointed Day of Judgment for all of the unsaved people of the world."

The website to which billboards direct readers says the initiative is backed by 89-year-old Harold Camping, author of the 1992 publication 1994?, which predicted the apocalypse for the year of the title, and We are almost there! which laid out his predictions for the years to come.

According to Camping, seven biblical signs have appeared that indicate the coming of the apocalypse, which will see the destruction of the world in October. The signs include the "re-establishment of National Israel in 1948."