Lord Sacks, Britain's former chief rabbi, has offered a prayer at a Vatican conference after militants killed at least four people in an attack on a synagogue in Jerusalem. Religious leaders from all over the world – including Muslim and Jewish leaders as well as Christians – paused for a moment to pray while at a conference on marriage. Two Palestinian men armed with a pistol, knives and axes stormed a seminary in West Jerusalem. Both of them were shot dead, police say. Israeli prime minister Benjamin Netanyahu has promised to respond "with a heavy hand to the brutal murder". US Secretary of State John Kerry described it as an act of "pure terror".