At least two merchant vessels reported they were hit by gunfire as they attempted to cross the Strait of Hormuz on Saturday, three maritime security and shipping sources said, shortly after Iran said it was once more tightening control of the waterway.

Earlier maritime trackers showed a convoy of eight tankers transiting the strait in the first major movement of ships since the U.S.-Israeli war on Iran began seven weeks ago.

But Iran then said it was reimposing strict military controls on the vital route, the conduit before the war of about a fifth of global oil trade, as the U.S. maintained its blockade of Iranian ports.

And in a defiant message posted on his Telegram channel, Iran's Supreme Leader Mojtaba Khamenei said Iran's navy was ready to inflict "new bitter defeats" on its enemies.

U.S. President Donald Trump hours earlier had cited "some pretty good news" about Iran, declining to elaborate. But he also said fighting might resume without a peace deal by Wednesday, when a two-week ceasefire expires.

Iran had announced its temporary reopening of the Strait of Hormuz following a separate U.S.-brokered 10-day ceasefire agreement on Thursday between Israel and Lebanon.

But on Saturday Iran's armed forces command said transit through the strait had reverted to a state of strict Iranian military control, citing what it described as repeated U.S. violations and acts of “piracy” under the guise of a blockade.

The spokesperson said Iran had earlier agreed, “in good faith,” to the managed passage of a limited number of oil tankers and commercial vessels following negotiations, but said continued U.S. actions had forced Tehran to restore tighter controls on shipping through the strategic chokepoint.

There was no immediate comment from the U.S.

(Reporting by Reuters bureaus, Writing by Raju Gopalakrishnan, William Maclean; Editing by William Mallard and Alex Richardson)