(CNN) - Iran said its Islamic Revolutionary Guard Corps held a naval exercise in the Strait of Hormuz last week "within the framework of their annual training program."
The exercise was held with aim of "controlling and maintaining the security of the international waterway of the Persian Gulf and the Strait of Hormuz, and to proportionately counter any threats by the enemy," semiofficial Tasnim news agency reported.
"Operation was part of IRGC's annual training program," Tasnim said. It said it included naval and aerospace units, and was described as "successful" by IRGC Chief Maj. Gen. Mohammad Ali Ja'fari,
Iran's actions in the globally significant waterway raised concerns last week after a US assessment found IRGC assembled a fleet of more than 100 boats and hundreds of Iranian troops were expected to participate.
CNN International Diplomatic Editor Nic Robertson witnessed more than 100 oil tankers anchored in the Gulf of Oman on Friday, waiting to enter the strait and load up with oil.
US officials said the major naval exercise was meant to demonstrate Iran's ability to shut down the Strait of Hormuz, which would have ripple effects across the globe.
The strait connects the Persian Gulf to the Arabian Sea. The US Energy Information Administration calls it "the world's most important oil transit chokepoint," with 20% of oil traded worldwide moving through the waterway, which is about 30 miles wide at its narrowest point.
The US military has been trying to encourage other nations in the region, especially Saudi Arabia, to take a strong line on keeping the Gulf open in the face of rising Iranian rhetoric. They have also expressed concern about keeping open the waterways off Yemen where Iranian-backed rebels have attacked oil tankers.
The Iranian military maneuvers are normally held later in the year and heavily publicized by Iran, Robertson reported. But this year's exercise was timed to take place as US prepares to reimpose sanctions on Iran after President Donald Trump pulled out of Iran nuclear deal.
Outrage by Iran's leaders when Trump took the decision in May is now being supercharged by small street protests against the government over the economy and the threat of more as the situation worsens.
The Iranian riyal is down 25% against the dollar. Monday, US sanctions will kick in, banning the purchase of US dollars, gold and other precious metals, and in early November oil, shipping and ports will be hit by the second phase of the same sanctions.
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