New Delhi, March 25 -- British police hunted three suspects on Tuesday over an arson attack on a Jewish charity's ambulances and pledged to step up security around a community that feels increasingly at risk.

The blaze in Golders Green, a London neighborhood with a large Jewish population, consumed four ambulances belonging to the volunteer organization Hatzola Northwest. Oxygen cylinders on the vehicles exploded, breaking windows in an adjacent apartment block. Also shattered was the community's shaky sense of security, already strained by wars in the Middle East and what many say is soaring hatred of Jews.

"We're feeling vulnerable," said Damon Hoff, president of the Machzike Hadath Synagogue, where the ambulances were parked. Some of...