By Iman Abu Hasira and Jana Shqeir

DUBAI/WASHINGTON, June 27 (Reuters) - Iran said on Saturday it had shelled targets linked to U.S. forces in retaliation for U.S. airstrikes on its southern coast, as the two sides traded accusations of violating an agreement reached this month aimed at ending the four-month-old war.

The Iranian Foreign Ministry did not specify the locations of its "defensive" attacks, which it said were a response to "brutal airstrikes" by the United States on Iranian coastal surveillance facilities, which it said also violated the UN Charter.

Bahrain, which hosts the US Navy's Fifth Fleet, later condemned what it described as an Iranian drone attack on its territory, calling it a flagrant violation of its sovereignty and a threat to its security, adding that it reserves the right to defend itself.

Washington has not yet responded to Iran's claims about striking American targets, a tactic Iran has used to undermine U.S. allies in the region during the conflict.

The U.S. military said its strikes on Friday were in response to an Iranian drone attack on a cargo ship in the Strait of Hormuz, a vital waterway for global energy supplies.

The United Kingdom Maritime Trade Operations (UKMTO) said on Saturday that a tanker reported being targeted by an unidentified projectile in the Strait of Hormuz.

The authority added that the ship sustained damage to the pilothouse, but all crew members were safe, noting that no environmental damage was recorded at the time of the incident.

Iran asserts its control over the vital strait

In a separate development, Israel and Lebanon signed an agreement to end the fighting between Israel and the Iranian-backed Hezbollah group. Both sides said the agreement represents an initial step calling on Hezbollah to lay down its arms and Israel to withdraw its forces from Lebanon, but it was unclear how it would be implemented. Hezbollah said it would not cooperate.

But the National News Agency reported on Saturday that an Israeli drone targeted the Nabatieh area in southern Lebanon.

Iranian state television said the Revolutionary Guard delivered a "decisive response" after US forces bombed a communications tower in the coastal city of Sirik. The Mehr news agency reported that the port was operating normally and no damage to facilities or equipment had been reported.

Bahrain said, "The Iranian regime's continued aggression, at a time when regional and international efforts are moving towards de-escalation, places the sole responsibility on Tehran for undermining peace efforts, and reveals an approach based on destabilizing security, exporting chaos, and undermining regional stability."

Bahrain accused Tehran of violating UN Security Council Resolution 2817 and the memorandum of understanding signed in Islamabad on June 17.

Following Thursday's attack on a cargo ship off the coast of Oman, Iran has not claimed responsibility. However, it has asserted its authority over maritime traffic in the Strait of Hormuz, stating that ships must adhere to routes designated by Tehran. It also warned Gulf states against siding with Washington, asserting that the interim agreement with the United States grants it control over shipping through the strategic waterway.

Ebrahim Azizi, head of the National Security Committee in the Islamic Consultative Assembly, said on Saturday that his country would respond firmly to any violation of Iran's instructions regarding navigation through the Strait.

The US Central Command said that what it considered an Iranian attack was "an unprovoked aggression against commercial shipping," adding that the United States would continue to provide "coordination and support for the safe passage" of commercial vessels through the strait - through which a fifth of the world's oil and liquefied natural gas supplies passed before Washington and Israel launched the war on February 28.

* Vance: "Violence for violence"

U.S. Vice President J.D. Vance said that the Americans have adhered to the ceasefire agreement, also called the Memorandum of Understanding.

Vance was previously seen as skeptical of US involvement in Iran, but he has now become the top official in charge of this conflict in the Trump administration.

Vance wrote on the X platform, "Iran signed the ceasefire agreement. We are committed to it. If they have objections about how the memorandum of understanding is to be implemented, they can call us. But violence will be met with violence."

Before the latest violence erupted, oil prices fell by about three percent on Friday, heading for sharp weekly losses as oil tankers left the Strait of Hormuz.

Shipping data showed that Saudi Aramco resumed loading crude oil at Ras Tanura, the world's largest oil port, after a nearly four-month hiatus. Fertilizer shipments through the strait also rebounded, helping to ease concerns about rising global food prices.

At the conclusion of his tour of the Gulf to reassure regional allies about the interim agreement, US Secretary of State Marco Rubio issued a joint statement with the Gulf Cooperation Council calling for "free and unconditional navigation" in the Strait, without transit fees or "attempts to impose control."

The Iranian Foreign Ministry said that the management of the Strait should be jointly between Iran and Oman, while Ali Akbar Velayati, a senior advisor to Iran's Supreme Leader, warned Washington's allies in the Gulf that "their survival depends on the extent of Tehran's tolerance."