In a friendly-fire incident, an Iranian missile hit a support ship, killing 19 of its sailors and injuring 15 others during a military drill in the Gulf of Oman, Iranian media disclosed on Monday.

The Oman Gulf is a highly critical channel as it leads to the Hormuz Strait - through which around 20 percent of the world's oil flows.

The Konarak support ship remained "very close" during the naval exercise, and was struck by a missile fired from another Iranian ship, state news agency IRIB reported.

The vessel had sunk after being struck by the missile, one article said. After shifting a practice target to its destination and not establishing enough space between itself and the target, the vessel was struck, the state television reported. The Iranian army said that "investigations" on the cause of the accident were underway. 

The Konarak is a light logistics support ship manufactured in the Netherlands which Tehran acquired before the Islamic Revolution of 1979. A local hospital admitted 12 sailors and treated three more with minor wounds, the state-run news agency IRNA said.

Iranian media said the Konarak was overhauled in 2018 and was able to fire sea and anti-ship missiles. The 47-meter (155-foot) Dutch-made combat vessel had been in operation since 1988 and had a capacity of 40 tons. It normally holds a 20-seat crew.

The Islamic Republic routinely conducts miliary drills in the area that is closed to the vital Strait of Hormuz, the narrow portal of the Persian Gulf. The 5th Fleet of the U.S. Navy which monitors the area has not responded immediately to a request for comment.

The incident happened at a time of heightened animosity between Tehran and Washington. Since 2018, when the US backed out of a 2015 nuclear agreement between major powers and Iran, frictions between arch foes have intensified and Washington has re-imposed sanctions on Tehran, crippling its economy.

Tensions between the two countries worsened in early January when the top Iranian military leader Qassem Soleimani was killed by a US drone attack in Baghdad. On January 9, Iran retaliated by firing rockets at Iraqi bases where US forces were deployed.

The friendly fire took place in the perimeter of the country's southern Jask port on the Gulf of Oman as the Iranian Navy conducted a naval exercise late Sunday, state TV reported. Iranian media rarely disclose mishaps during its military exercises, signaling the severity of the incident.