(Reuters) – The U.S. struck Iran’s coastal defenses and missile sites on Wednesday after reimposing a naval blockade of its ports, while Iran threatened to shut ​off more regional energy exports, saying it was engaged in an “existential war” with America.

The latest escalation of attacks and counterattacks launched by the U.S. and Iran has kept the region on edge days a fragile truce collapsed, raising the spectre of a return to full-scale war, though analysts generally see that as less likely.

Hostilities have intensified since Iran said late on Saturday it had closed the Strait of Hormuz. The ongoing military operations are also keeping ships from transiting the vital artery, which carried about a fifth of global oil and gas shipments before the war. Brent crude oil, the international benchmark, closed at a one-month high at $84.95 a barrel on Wednesday.