Sri Lanka, April 13 -- The deadline passed on Monday for the start of a U.S. military blockade of ships leaving Iran's ports, and Tehran threatened to retaliate against ports of its Gulf neighbours after weekend talks on ending the war broke down.

Oil prices surged, with no sign of a swift reopening of the Strait of Hormuz to ease the biggest ever disruption in supplies.

Since the war started on February 28, Iran has effectively shut the strait to all vessels except its own, saying passage would be permitted only under Iranian control and subject to a fee.

U.S. President Donald Trump said Washington would block Iranian vessels and any ships that paid such tolls and that any Iranian "fast-attack" ships that went near the blockade would ...