Iran's new supreme leader, Mojtaba Khamenei, said Thursday that the closure of the Strait of Hormuz maritime passage should be continued as a "tool to pressure the enemy," in his first public statement since being appointed.

Khamenei also said all U.S. military bases in the Middle East should close immediately and "those bases will be attacked," in televised comments translated by Reuters.

Oil prices extended gains following the statement, read out by a state TV broadcaster. The shipping of oil through the Strait of Hormuz has effectively stopped since the war began, causing global oil prices to soar. Iran warned on Wednesday that the price per barrel could climb to $200.

It's Khamenei's first public comments since being appointed as Iran's supreme leader on March 9 after the assassination of his father, Ayatollah Ali Khamenei, in U.S.-Israeli air strikes which began in late February.

Mojtaba Khamenei was injured in the attack on his father's compound, which killed the ayatollah and other immediate members of the family.

"Iran will not refrain from avenging the blood of its martyrs," Khamenei said, calling for unity among the Iranian people.

Khamenei, 56, is seen as more hard-line and conservative than his father, although he kept a low profile in Iran before he was elected to succeed him as supreme leader.

U.S. President Donald Trump expressed "disappointment" in his selection by Iranian senior clerics, telling Fox News, "I don't believe he can live in peace."

Despite Trump's comments, it's unclear whether the White House is aiming for regime change in Tehran as one of its main objectives in its military operation. Experts have said that airstrikes alone are unlikely to be enough to unseat Iran's leadership.

There are no signs that the U.S.-Israeli strikes on Iran's critical and military infrastructure are nearing a conclusion, with air and sea attacks intensifying this week. Iran has also stepped up its retaliatory assaults this week, attacking tankers in or near the Strait of Hormuz.

Khamenei said Thursday that Iran will seek compensation from enemies "or destroy their assets accordingly."