The Latest: Iran's FM says UK ship was traveling unsafely Iran's foreign minister says his country seized a British-flagged oil tanker last week because it was violating "international law on safe passage" in the Strait of Hormuz

DUBAI, United Arab Emirates -- The Latest on tensions in the Persian Gulf (all times local):

11:30 p.m.

Iran's foreign minister says his country seized a British-flagged oil tanker last week because it was violating "international law on safe passage" in the Strait of Hormuz.

Speaking Monday during a visit to Nicaragua, Mohammad Javad Zarif said the British ship had "turned off its signaling" for longer than is allowed, and "was passing through the wrong channels."

Iranian officials have previously suggested the Stena Impero was seized and taken to an Iranian port in response to Britain's role in seizing a supertanker carrying Iranian oil two weeks earlier.

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8:15 p.m.

Britain says it is joining with European allies to form a "maritime protection mission" in the Strait of Hormuz following Iran's seizure of a U.K.-flagged oil tanker in the busy waterway.

Foreign Secretary Jeremy Hunt called the seizure of the Stena Impero and its 23 crew "an act of state piracy."

Hunt gave no details of the new mission, but said Britain would "take appropriate action to support the safe passage of vessels through the Strait of Hormuz."

He stressed that Britain's moves were not part of the United States' policy of "maximum pressure" on Iran. European nations still adhere to the international nuclear deal with Iran that the U.S. has withdrawn from.

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6:40 p.m.

The husband of a British-Iranian woman imprisoned in Iran says she has been transferred from a hospital mental health facility back to prison.

Richard Ratcliffe said Monday that his wife, Nazanin Zaghari-Ratcliffe, had been kept in solitary confinement and chained to a hospital bed. He says she described the treatment as "proper torture."

He says she was returned to Evin prison Saturday after breaking out of her bindings and telling security guards she could self-harm if she stayed in the hospital.

The news comes amid heightened tensions between the U.K. and Iran over the seizure of a British-flagged oil tanker in the Persian Gulf.

The 40-year-old Zaghari-Ratcliffe was arrested in Iran April 2016 and has been sentenced to five years in prison after being accused of spying, which she strongly denies.

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6:00 p.m.

President Donald Trump says Iran's claim that it arrested 17 Iranian nationals recruited by the CIA to spy on the country's nuclear and military sites is "totally false."

Iran said Monday the arrests were made in recent months and some of the individuals have been sentenced to death.

Trump tweeted that there is "zero truth" to the claim.

U.S.-Iran relations have spiraled downward and tensions have spiked in the Persian Gulf. Iran's economy is suffering from crippling economic sanctions imposed after Trump last year pulled the U.S. out of Iran's nuclear accord with world powers.

He says Iran is a "total mess" and that the government is failing and doesn't know what to do.

Secretary of State Mike Pompeo declined on Monday to address specifics of the arrests, but says "the Iranian regime has a long history of lying."

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4:25 p.m.

Iran's state broadcaster has released new video showing for the first time the 23-member crew of the British-flagged ship seized by Iran — an apparent attempt to convey they are safe and unharmed.

In the video aired Monday, the Stena Impero crew is seen dressed in red uniforms and seated around a table onboard the vessel as an unidentified Iranian man is heard thanking them for their cooperation. A cameraman is heard telling them not to look at the camera.

It wasn't clear if the crew was under duress to take part in the filming.

Other choreographed shots show a man checking on the ship, the crew sharing a laugh and talking next to a coffee machine inside the ship. The crew's chefs are seen preparing food. Another video, also released by Iran's state broadcaster, shows Iran's flag hoisted on the ship's bridge.

The ship was seized Friday in the Strait of Hormuz. None of the crew are British nationals but are mostly Indian and also Filipino, Russian and Latvian nationals.

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3:45 p.m.

China says it will "actively consider" sending a delegation to Vienna to discuss the Iran nuclear issue next week.

Chinese Foreign Ministry spokesman Geng Shuang said on Monday that China is "maintaining close communications with other parties" about the planned meeting.

He added that "China has repeatedly stressed that ensuring the full implementation" of the Iran nuclear deal is "the only viable and effective way" to resolve the issue and ease tensions.

Since the U.S. unilaterally pulled out of the deal last year, the other parties to the agreement — China, Germany, France, Britain, Russia and the European Union — have been trying to preserve it.

The U.S. has imposed sanctions on Chinese and other entities for allegedly helping Iran buy materials for its nuclear program.

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3:30 p.m.

Germany's Foreign Minister Heiko Maas says the country will not follow President Donald Trump's approach to Iran, instead prioritizing de-escalation through diplomacy.

Maas said in Paris on Monday that Germany does not want to join in the U.S.'s maximum-pressure strategy.

Following discussions with British Foreign Secretary Jeremy Hunt on Sunday and French Foreign Minister Jean-Yves Le Drian on Monday, the German diplomat said that alongside handling the dangers in the Strait of Hormuz, Europe will continue to play the "diplomatic card".

He said that "what we need is de-escalation, and my British and French colleagues have the same opinion."

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11:30 a.m.

Iran says it has arrested 17 Iranian nationals allegedly recruited by the Central Intelligence Agency to spy on the country's nuclear and military sites, and some of them have already been sentenced to death.

An Iranian intelligence official told a press conference on Monday in Tehran that the arrests occurred over the past months. He did not say how many got the death sentence.

The announcement comes as Iran's nuclear deal with world powers is unraveling and tensions spike in the Persian Gulf region.

The official did not give his name but was identified as the director of the counterespionage department of Iran's Intelligence Ministry. Such a procedure is highly unusual in Iran; officials usually identify themselves at press conferences.

The official said some of those arrested worked in nuclear and military sites. He claimed none had succeeded in their sabotage missions.

—Nasser Karimi in Tehran, Iran;

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9:55 a.m.

British Prime Minister Theresa May will chair an emergency security session to discuss how to respond to Iran's seizure of a British-flagged tanker in the Strait of Hormuz.

The meeting of security ministers and officials on Monday will discuss how to secure shipping in the sensitive region, which is vital to the world's oil supply.

Foreign Secretary Jeremy Hunt is also expected to brief Parliament on the Friday seizure of the Stena Impero tanker, now in a heavily guarded Iranian port.

Britain is considering a number of options to raise the pressure on Iran but officials say military operations are not being considered at the moment.

Britain is also seeking diplomatic and operational support from key European allies in an effort to keep the Strait of Hormuz open to shipping.