Iran said it would hold the US responsible for any clashes in the Gulf. It also threatened to impose sanctions on 15 US companies for their support for Israel and its “terrorist actions.”

Separately, Iran’s central bank said it would appeal Luxembourg’s decision to freeze $1.6 billion of its assets.

Iran denied US accusations that its fast-attack boats were “harassing” warships at the mouth of the Arabian Gulf. US Navy commanders had accused Iran of jeopardizing international navigation by “harassing” warships passing through the Strait of Hormuz. They said future incidents could result in miscalculation and lead to an armed clash.

Brig. Gen. Masoud Jazayeri, deputy chief of staff of Iran’s armed forces, said the US claims of the confrontation in the Gulf were based on “false reports or ulterior motives,” the state news agency IRNA reported.

“We emphasize that the Americans would be responsible for any unrest in the Arabian Gulf, and again warn that the US military must change its behavior,” Jazayeri said, without elaborating.

US commanders earlier said Tuesday’s incident, in which the USS George H.W. Bush sent helicopter gunships to hover over the Iranian speedboats as some came as close as 870 meters from the aircraft carrier, ended without a shot being fired.

But it underscored growing tension between the US and Iran since the election of Trump, who has condemned the 2015 nuclear deal that his predecessor Barack Obama and leaders of five other world powers struck with Tehran and labeled the Islamic republic “the number one terrorist state.”

The decision to sanction US companies, which is largely symbolic because the firms do not do business with Iran, comes two days after the US announced new sanctions on a number of foreign firms accused of collaborating with Iran’s weapons program.

Iran’s sanctions target US firms that provide arms and equipment to Israel “for use against the Palestinians,” IRNA said.

Meanwhile, Luxembourg’s decision to freeze $1.6 billion of Iranian assets is seen as a response to US claiming of the assets as compensation for victims of the Sept. 11, 2001, attacks.

A Luxembourg court last week denied Tehran’s request to retrieve the $1.6 billion frozen in the country during an earlier raft of sanctions targeting Iran’s nuclear program.

The encounter with Iranian Navy boats occurred as the USS George H.W. Bush was en route to the northern part of the Gulf to participate in US-led airstrikes against Daesh militants in Iraq and Syria.

Earlier in March, Iran disputed the US account of another confrontation in the Strait of Hormuz between its speedboats and a US Navy vessel.

-Agencies