The US has begun a new wave of strikes against Iran after reimposing a naval blockade of Iranian ports, while Tehran threatens to shut off more regional energy ‌exports.

The strikes mark the latest escalation of attacks and counterattacks launched by both warring sides as they vie for control of the Strait of Hormuz, which carried about a fifth of global oil and gas shipments before the war.

“At 3pm ET today, U.S. forces launched operations for a second wave of strikes today against Iran,” US Central Command said on Thursday.

The fresh wave followed a daytime raid that followed a fourth night of US airstrikes.

In a statement issued hours after the Iranian Mehr news agency reported that US projectiles had hit a location on Iran’s Hengam Island in the strait, Iran’s top negotiator Mohammad Baqer Qalibaf ‌said Iranian security depended on ‌maintaining what he called “Iranian arrangements” in the strait.

“We ⁠are in an essential and existential war with America,” Qalibaf said.

Late on Tuesday (local time), the US military said it had hit dozens of military targets near the Strait of Hormuz and Iranian ⁠coastal areas in strikes lasting seven hours.

In response, Iran’s ‌Islamic Revolutionary ​Guard Corps said on Wednesday it had struck US military targets in the region, including in Bahrain, ​Kuwait and ‌Jordan.

It also threatened on Wednesday to shut off more regional energy exports, saying the US “must brace ​for the closure of all other export corridors that benefit the US and its allies”.

Meanwhile, when asked whether he was giving Iran a deadline before bombing bridges, US President Donald Trump said “they better behave”.

“I don’t like giving deadlines, but they pretty much know – they know the story,” he said.

The US has said Iran had attacked seven commercial ships in the past week, leading to ​nearly ​a dozen crew members being killed, missing ​or injured.

Oil prices extended gains by about 1 per cent on Wednesday, after settling on Tuesday on a new one-month high.

An interim ​ceasefire deal in the conflict signed last month was meant to lead to further negotiations ​and a permanent truce, but ⁠a return to talks has faltered.

—with AAP