DUBAI — An Iranian surface-to-air missile shot down a U.S. military surveillance drone Thursday in international airspace over the Strait of Hormuz in an "unprovoked attack," U.S. officials said, disputing Iranian reports that the aircraft was over its territory.

The downing came amid rising tensions between Washington and Tehran since the Trump administration's decision to withdraw from the 2015 Iran nuclear agreement last year. The U.S. has accused Iran of recent attacks on oil tankers in the Persian Gulf region, allegations the Iranians deny.

"U.S. Central Command can confirm that a U.S. Navy Broad Area Maritime Surveillance (or BAMS-D) ISR aircraft was shot down by an Iranian surface-to-air missile system while operating in international airspace over the Strait of Hormuz at approximately 11:35 p.m. GMT on June 19, 2019," Navy Capt. Bill Urban, U.S. Central Command spokesman, said in a statement.

Brent crude jumped on the news in early morning trading, up 2.86%, or $1.77, at $63.59 a barrel at 7:50 a.m. ET. The U.S. benchmark West Texas Intermediate was up 3.55%. The Strait of Hormuz is a critical conduit for 30% of the world's seaborne oil.

The downing was first announced by Iran's Islamic Revolutionary Guards on its website, Sepah News. The Iranian outlet claimed the Revolutionary Guards had shot down a U.S. "spy drone" over the southern province of Hormozgan.

"The downing of the American drone was a clear message to America. ... Our borders are Iran's red line and we will react strongly against any aggression," Major Gen. Hossein Salami, the recently appointed chief of Iran's elite Islamic Revolutionary Guard Corps, told Iranian state TV. "Iran is not seeking war with any country, but we are fully prepared to defend Iran."