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The Latest on Mideast developments amid rising tensions in the Persian Gulf region (all times local):

10 a.m.

A U.K. maritime safety group is warning that an unspecified incident has taken place in the Gulf of Oman and is urging "extreme caution" amid heightened U.S.-Iran tensions.

The United Kingdom Maritime Trade Operations, which is run by the British navy, put out the alert early on Thursday. It did not elaborate but said it was investigating.

The U.S. Navy's Bahrain-based 5th Fleet did not immediately respond to a request for comment.

The incident comes as Iranian media claimed — without offering any evidence — that there had been an explosion in the area targeting oil tankers.

Thursday's maritime alert comes after what the U.S. has described as Iranian attacks on four oil tankers nearby, off the coast of the United Arab Emirates. Iran has denied being involved.

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9:35 a.m.

Japan's top government spokesman says Prime Minister Shinzo Abe's high-stakes trip to Iran is intended to help de-escalate tensions in the Mideast — and not specifically mediate between Tehran and Washington.

The remarks by Chief Cabinet Secretary Yoshihide Suga to reporters were apparently meant to downplay and lower expectations amid uncertain prospects for Abe's mission.

Abe was to meet with Iran's Supreme Leader Ayatollah Ali Khamenei on Thursday, the second and final day of his visit.

On Wednesday, after talks with Iranian President Hassan Rouhani, Abe warned any "accidental conflict" that could be sparked amid the heightened U.S.-Iran tensions must be avoided.

Tensions have escalated in the Mideast and Iran appears poised to break the 2015 nuclear deal with world powers. Washington pulled out of the agreement last year.