State Department tells Americans worldwide to 'exercise increased caution'

A vessel was struck by an "unknown" projectile about 4 nautical miles east off the coast of Ras Laffan, Qatar, the U.K. Maritime Trade Operations Center said in a warning posted early on Thursday.

"All crew are reported safe and well," according to the UKMTO, a marine monitoring organization that works with merchant shipping and military forces in the region.

Iran on Wednesday had launched retaliatory strikes that included the targeting of a liquified natural gas terminal in Ras Laffan, an industrial hub on the Persian Gulf.

The UKMTO warning, which was tagged as "suspicious activity," came several hours after the UKMTO said another vessel was similarly struck about 11 nautical miles east of Khawr Fakken, the United Arab Emirates, causing a fire onboard.

The UKMTO did not publish details about either of the ships struck overnight. It was not immediately clear what type of projectile had struck either vessel.

"Since the start of the hostilities on 28 February, more than twenty incidents involving commercial vessels and offshore infrastructure have been reported across the Arabian Gulf, Strait of Hormuz, and Gulf of Oman," the UKMTO said in an advisory note published on Wednesday.

As the U.S. and Israel have struck Iran this month, Tehran has vowed to close the Strait of Hormuz, a vital shipping channel off its southern coast, to most ships. Iranian officials have claimed to have launched attacks on several ships traveling in or near the strait.

"The incidents involve a wide range of vessel types and flag states, with no consistent pattern of Western ownership linkage," the UKMTO said on Wednesday, "suggesting that the current strike patter reflects a campaign aimed at broad maritime disruption rather than selective vessel targeting."

President Donald Trump in a social media post late Wednesday night, called for Israel to not attack the South Pars Gas Field unless Iran again attacks Qatar's liquefied national gas facilities.

“NO MORE ATTACKS WILL BE MADE BY ISRAEL pertaining to this extremely important and valuable South Pars Field unless Iran unwisely decides to attack a very innocent, in this case, Qatar,” Trump said.

Trump said if Iran does so, the U.S. will respond and “massively blow up” the South Pars gas field.

"I do not want to authorize this level of violence and destruction because of the long term implications that it will have on the future of Iran, but if Qatar’s LNG is again attacked, I will not hesitate to do so," Trump said in the post.

Trump began his post saying the U.S. was not made aware in advance of Israel’s attack on South Pars on Wednesday, an escalation in the conflict.

Trump also claimed that Qatar was also not aware Israel would strike the Iranian gas field.

“The United States knew nothing about this particular attack, and the country of Qatar was in no way, shape, or form, involved with it, nor did it have any idea that it was going to happen,” Trump wrote.

Iranian state media said Wednesday that Israel attacked Iran’s South Pars Gas Field, one of the nation’s largest gas resources and a key lifeline for Iran.

The Senate once again rejected an Iran war powers resolution, the second the chamber has considered this month.

The resolution would direct the removal of United States Armed Forces from hostilities within or against Iran that have not been authorized by Congress. Because the resolution was privileged, it only would have needed the support of 51 senators to advance. Still, the resolution was blocked by a vote of 47-53.

Sen. John Fetterman was the only Democrat to vote against the resolution. Sen. Rand Paul was the only Republican to vote for it.

-ABC News' Allison Pecorin

Gas facilities near Abu Dhabi have been shut down due to falling debris from the interception of missiles, the Abu Dhabi media office said.

The missiles targeted the Habshan gas facilities and the Bab oil field, according to the office, which said operations at the gas facilities have been suspended.

No injuries have been reported, the office said.

The United Arab Emirates' Ministry of Foreign Affairs said it "strongly condemned the Iranian terrorist attack" targeting facilities and that the attacks "constitute a dangerous escalation and a violation of international law."