The threat to ships carrying oil in the Middle East is at its worst since the Iran war started, experts have said, after a spate of attacks on another key route in the region.

The warning comes after a number of attacks on vessels in the Red Sea, an alternative waterway that some tankers had been using since Iran blocked the Strait of Hormuz.

Iran has denied Donald Trump’s claim that it was in talks with the US over reopening the strait, but said it was speaking to Oman about securing the shipping lane.

“In terms of threat to the trade of crude, we’re at the worst period that we’ve been in since this since this crisis began,” said Matthew Wright, an analyst at ship-tracking firm Kpler.

The number of ships passing through the Strait of Hormuz was just eight on Sunday and 11 on Saturday, compared with more than 100 per day before the war began, according to Kpler.

Before the conflict, about 20% of the world’s oil and gas passed through the strait.

The temporary peace deal with the US struck in early June led to numbers rising again, but the resumption of strikes between the two countries roughly a month later have significantly reduced traffic.

Many ships have been “going dark” when crossing the strait, meaning they turn off their transponder to avoid detection.

For much of the war, some ships carrying oil from Saudi Arabia had instead passed through an alternative shipping lane in the Red Sea, between the kingdom and west Africa.

But a recent spate of attacks by Yemen’s Houthi fighters on Saudi tankers using the alternative waterway has further heightened the risks.