Iran’s Revolutionary Guard (IRGC) said it fired ballistic missiles at a base in Jordan used by the US military and attacked 10 ships on Wednesday, after the US said it had destroyed five Iranian oil tankers, in a sharp escalation of the six-month-old war.

Increased attacks by both the US and Iran have shattered a month of relative calm, hitting military, shipping and energy assets, sending oil prices surging and drawing in regional allies in recent days.

The US military’s Central Command posted video of the strikes, which it called a response to IRGC targeting a US Navy warship twice with ballistic missiles over the previous two days. No Americans were harmed, the US said.

“Iran continues to try to hit US naval ships, and for every time they do that or try to do that, they’re going to lose tankers,” US Secretary of State Marco Rubio told reporters during a visit to Colombia.

Iran then carried out a ballistic missile attack on a base used by US forces near Al Azraq in Jordan, according to an IRGC statement on state media.

Although Iran said its missiles inflicted heavy damage, Jordan said its air defences intercepted 18 of the 20 Iranian missiles, with two falling in unpopulated areas, and that there were no casualties.

A US official said Iran’s strikes in Jordan were ineffective and all American troops were accounted for.

The IRGC said on Wednesday it also attacked 10 ships, including two US Vessels and eight oil tankers, attempting to cross a “prohibited and unsafe” area of the Strait of Hormuz, a vital energy conduit largely choked off by Iranian attacks.

Iran has targeted US assets and allies in the region throughout the war, including in Jordan several times, killing at least two US military personnel during one strike in July.

Iran has also threatened oil tankers in Kuwaiti and Bahraini ports, according to a statement carried by state media. A maritime security source reported a liquefied natural gas tanker was damaged in the Emirati port of Khor Fakkan, though it was unclear who was responsible.

Oil prices extended gains in early trade on Wednesday with Brent crude nearing $100 a barrel on market concerns over the disruption of oil tanker traffic in the Strait of Hormuz.

Recent attacks by Yemen’s Houthis on top energy producer Saudi Arabia have added to supply concerns.

Houthi attacks on Saudi Arabia

On Tuesday, Houthis launched an attack on several cities in Saudi Arabia, further undermining regional stability.

The Houthi attacks wounded 73 people and set oil installations ablaze in what appeared to be a major expansion of the conflict, which began on February 28 with joint US-Israeli attacks on Iran.

The Houthis, who control most of Yemen’s populated areas, including the capital, have further pressured US allies by periodically disrupting shipping on the other side of the Arabian Peninsula, at the entrance to the Red Sea.

They said they had launched a broad operation deep into Saudi territory, using drones and missiles to strike a Saudi air base in the southern city of Khamis Mushait as well as Saudi state oil company assets in the cities of Abha, Najran and Jazan.

Saudi authorities reported blazes at the sites and said women and children were among the wounded.

The wider war in the Gulf has turned into a test of wills between the US and Iran, with each side hoping that economic pressure from competing blockades will force the other to yield.

Washington is trying to increase the flow of oil to world markets by guiding ships through the Strait of Hormuz, while cutting off Iran’s exports with a blockade.

Central Command said the tankers it destroyed on Tuesday were part of a shadow network that funds the IRGC and its regional proxies.