The U.S. Embassy (search) has received "credible reports" of plans to kidnap U.S. citizens in Gaza, the Embassy announced on its Web site Friday.

"At this time, Americans are advised to be particularly cautious," the announcement said, adding that citizens should also follow already-existing recommendations on the site to defer travel to Israel, the West Bank, and Gaza (search).

The Islamic militant groups Hamas (search) and Islamic Jihad (search) are mainly based in Gaza. Both groups have claimed responsibility for scores of attacks in Israel that have killed more than 350 people in the past 32 months of Israeli-Palestinian violence.

"Ongoing violence has caused numerous civilian deaths and injuries, including to some American tourists, students and residents," the already-existing travel advisory stated. "The potential for further terrorist acts remains high."

The advisory urges all American citizens in the West Bank, Gaza and Jerusalem to "consider relocating to a safe location," or to avoid crowded public places such as malls, restaurants, bus stops that have been targets for suicide-bomb attacks by the militants.

The warning also came after the deadly May 12 attacks on three housing compounds for foreigners in Saudi Arabia and a deadly series of attacks in Morocco on May 16.