Dubai: Iraninfo-icon Friday seized a British-flagged oilinfo-icon tanker and briefly detained a second vessel in the Strait of Hormuzinfo-icon, three weeks one of its vessels was captured by British navy off the coast of Gibraltar intensifying tensions in the strategic waterway that has become a flashpoint between Tehraninfo-icon and the West.

Iran has taken the 30,000-tonne UKinfo-icon-flagged Stena Impero tanker to Bandar Abbas port, where it and its crew will remain while an investigation into the vessel's conduct is carried out, officials said on Saturday.

The Iranian seizure came on the day Britaininfo-icon controlled Gibraltar government extended by 30 days the detention of the Iranian tanker loaded with over 2 million barrels of crude oil.

Islamic Revolutioninfo-icon Guards Corps (IRGC) impounded Stena Impero on Friday when it was passing through the Strait of Hormuz en route to Saudi Arabiainfo-icon "for failing to respect international maritime rules."

Late on Friday, the British government advised UK ships "to stay out of" the Strait of Hormuz "for an interim period."

The ongoing showdown has caused jitters around the globe, with each manoeuvre bringing fear that any misunderstanding or misstep by either side could lead to warinfo-icon.

Iranian authorities say the British oil tanker was involved in an accident with an Iranian fishing boat and had ignored its distress call before capture.

Morad Afifipoor, head of Ports and Maritime Organization, said on Saturday that the Brtish tanker had "collided with an Iranian fishing boat on its route and, according to law, after an accident it is necessary that the causes are investigated."

Afifipoor also noted that the British tanker and its crew, 23 of them Indian, will remain in its custody while a probe is carried out into its conduct. 

The United Statesinfo-icon said it was sending military personnel and resources to Saudi Arabia for the first time since the U.S. invasion of Iraqinfo-icon in 2003 in response to the escalating tensions.

An unnamed military official informed said the British ship had breached international maritime regulations by passing through a prohibited maritime passage in the Strait, turning off its tracking signals and ignoring warnings issued by Iranian authorities.

"The tanker had turned off its tracker and ignored several warnings by the IRGC before being impounded," IRNA quoting the source reported.

An informed official from Iran's Ports and Maritime Organization said that in addition to the previously-stated infractions, the vessel had also been "releasing oil residue from its tankers in the Persian Gulfinfo-icon".

The unnamed Iranian maritime official stressed that the ship's numerous infringements counted as a violation of the concept of "innocent passage," referring to a maritime law related to the passage of vessels through the territorial waters of another state.

Richard Weitz, a security analyst at Wikistrat, a global risk consultancy group, said Friday's incident was a "recipocral action" by Iran.

The UK has featured prominently in the recent tensions with Iran. Britain's Royal Marines assisted in the seizure of an Iranian oil supertanker on July 4 by Gibraltar, a British overseas territory off the southern coast of Spaininfo-icon.

On Friday, Gibraltar's Supreme Courtinfo-icon extended for 30 days the detention of the seized Iranian supertanker, Panama-flagged Grace 1, which was intercepted off the southern tip of Spain on July 4.

Following the Iranian action, the British government convened a major emergency cabinet meeting with COBRA officials present to assess the Friday's developments.

Foreign Secretary Jeremy Hunt has said that a second vessel was also impounded. He described the capture of both tankers as "unacceptable".

However Iranian military sources said the second British-owned Liberian-flagged tanker, the Mesdar, was allowed to continue its pre-scheduled course after "being briefed on the concept of innocent passage and observing environmental regulations".

British Foreign Secretary Jeremy Hunt initially said two ships were seized Friday in the Strait of Hormuz, the second sailing under a Liberian flag.

The owner of the Liberian-flagged tanker later said the ship was briefly boarded by armed guards before being allowed to go.

The Friday's incidents came two days after Washington claimed that a USinfo-icon warship downed an Iranian drone in the strait. Iran denied that it lost an aircraft in the area.

Iran released footage captured by an IRGC drone flying over and monitoring a US Navy vessel, belying a claim by Washington that the unmanned aircraft was shot down by the American forces.

The IRGC's Public Relations Department said Friday that the footage had been released with the aim of exposing Washington's "lies."

On June 20, Iran shot down an American drone in the same waterway, and Trump came close to retaliating but called off an airstrike at the last moment.

Tensions in the region have been escalating since Trump withdrew the US last year from Iran's 2015 nuclear deal with worldinfo-icon powers and imposed sweeping economic sanctions on Iran, including its oil exports. The sanctions have hit the Iranian economyinfo-icon hard.