UPDATE | US official names Americans killed at synagogue

LONDON (AP) — The U.S. State Department has identified three Americans among those killed in an attack today at a synagogue in Israel.

Spokeswoman Jen Psaki named the three U.S. citizens as Mosheh Twersky, Aryeh Kupinsky and Cary William Levine.

Secretary of State John Kerry, traveling in London, condemned the attack on "innocent people who had come to worship."

Kerry demanded that the Palestinian leadership take immediate steps to end incitement to violence as Israeli-Palestinian tensions soared.

"This morning in Jerusalem, Palestinians attacked Jews who were praying in a synagogue," he said shortly after Israeli authorities reported that two Palestinians had stormed the synagogue, attacking worshipers with knives, axes and guns, and killed four people before being killed in a shootout with police.