WASHINGTON: The Pentagon will bolster defensive posture in the Gulf region because Iran has increased its attacks on commercial shipping in recent months, White House spokesperson John Kirby said on Friday.

In the past two years, Iran has `harassed, attacked or interfered with the navigational rights` of 15 internationally flagged commercial vessels, Kirby said.

`Today, the Department of Defence will be making a series of moves to bolster our defensive posture in the Gulf,` Kirby told reporters in a briefing.

Kirby said US Central Command would provide details in coming days.

The move comes after Iran seized a second oil tanker in a week in Gulf waters earlier this month, and the State Department called for its release in the latest escalation in a series of actions against commercial vessels in Gulf waters since 2019.

The Bahrain-basedFifth Fleet of the US Navy said on May 3 the Panamaflagged oil tanker Niovi was seized by Iran`s Islamic Revolutionary Guard Corps Navy while passing through the Strait of Hormuz. The incident came days after Iran seized a Marshall Islandsflagged oil tanker in the Gulf of Oman.

Kirby said the US strongly condemns actions that threaten and interfere with commercial shipping, and will not allow foreign powers to jeopardise navigating Middle East waterways.

`We have seen repeated Iranian threats, armed seizures and attacks against commercial shippers who are exercising their navigational rights and freedoms in international waterways,` he said.

About a fifth of the world`s crude oil and oil products passes through the Strait of Hormuz, a choke point between Iran and Oman, according to data from analytics firm Vortexa.-Reuters