To add details

From Yumna Ehab and Phil Stewart

Cairo/Washington, June 28 (Reuters) - Iran and the United States continued their attacks in the Gulf region, each accusing the other of violating the interim agreement signed less than two weeks ago to end their four-month-long war.

Shortly after President Donald Trump warned that the United States might "finish the job militarily," Iran launched missiles and drones early Sunday at U.S. military sites in Kuwait and Bahrain, continuing its escalating attacks.

The US military had earlier said it launched a new attack on Iran hours after targeting an oil tanker in the Strait of Hormuz, the world's most important energy waterway, which Iran has kept largely closed since the start of the conflict.

The 14-point interim agreement between the United States and Iran was supposed to halt the fighting that the United States and Israel began on February 28, and reopen the strait to maritime traffic until talks could begin on deeper issues such as Iran’s nuclear program.

Violence and accusations erupted after an agreement and talks.

A round of talks involving mediators, led by US Vice President J.D. Vance and Iranian Parliament Speaker Mohammad Baqer Qalibaf, was held in Switzerland a week ago, and Washington lifted sanctions on Tehran. However, fighting and accusations have resumed and intensified since then.

Trump wrote on social media, "There may come a time when we are no longer able to act rationally, and we will have to complete the mission militarily after we started it so successfully. If that happens, the Islamic Republic of Iran will not exist."

About an hour after Trump's post, the Kuwaiti military said its air defenses were responding to attacks by "hostile" missiles and drones, while Bahrain's Interior Ministry reported that sirens sounded in the country.

Iran’s Revolutionary Guard said its naval and air forces launched joint missile and drone operations targeting US military sites in Kuwait and Bahrain in response to the latest US strikes on Iran.

A U.S. official confirmed the attacks on the facilities, saying the situation was still developing, but there were no reports of American casualties or significant damage to U.S. sites in the Middle East at this time.

The state-run Press TV quoted the Revolutionary Guard as saying in a statement that the US strikes violated the ceasefire and would "lead to a complete halt to all diplomatic operations." The statement added that US bases in the region "will see hell in the coming days."

The US Central Command said earlier that its forces launched new strikes after a Panamanian-flagged tanker was attacked by an Iranian drone on Saturday.

The Central Command said in a statement, "Iran had the opportunity to abide by the ceasefire agreement, but chose not to." It added that the strikes came "in direct response to Iran's continued aggression against commercial shipping," and that they targeted Iranian military surveillance, communications, air defense, drone storage, and mine-laying facilities.

Iranian state television reported early Sunday that explosions were heard in the southern Iranian city of Sirik, without providing further details. The Revolutionary Guard stated, "The random American fire on Sirik will not diminish our control over the Strait of Hormuz, but firing on violators will remind other ships of the importance of a safe passage."

* Focus on the strait and the fragile ceasefire in Lebanon

The tanker was targeted on Saturday in the strait following an attack on a cargo ship on Thursday, marking the latest escalation in the situation. Iran made a renewed attempt to assert its control over the world's most important energy shipping lane, which had reopened in the past two weeks after being closed for months.

Hundreds of ships, including oil tankers, have been trapped inside the Gulf since the war began. As they began to exit through the strait over the past two weeks, oil prices have fallen to near pre-war levels due to increased supply.

Washington is promoting a southern route along the coast of Oman, while Tehran wants ships to take a northern route through its waters and under its control, as it ultimately aims to impose fees for the use of the strait.

Iran accused the United States of violating the interim agreement, specifically by failing to uphold its commitment to a ceasefire in Lebanon, which Israel invaded in March to pursue the Tehran-backed Hezbollah group.

Israel and Lebanon have repeatedly agreed to ceasefires brokered by the United States, most recently on Friday. However, these agreements have generally had only a limited impact, as Israel insists on not withdrawing from the territories it has seized, while Hezbollah refuses calls to disarm as long as Israeli forces remain stationed in southern Lebanon.

While hundreds of thousands of Lebanese, mostly Shiites, are still unable to return to their homes in the occupied areas, anger over the agreement has spread to the wider Shiite community, as it is no longer limited to Hezbollah alone.