(Reuters) - Iran’s Revolutionary Guards warned the United States about its military activities in the Gulf on Sunday, adding that their navy had as a result increased patrols, which would also secure the passage of Iranian ships and combat fuel smuggling.

The U.S. military said on Wednesday that 11 Revolutionary Guards naval vessels had come close to its navy and Coast Guard ships, describing the moves “dangerous and provocative”.

The Guards’ statement on Sunday, which said Iran will give a decisive response to any mistake by the United States in the Gulf, provided the first confirmation of the incident.

“We advise the Americans to follow international regulations and maritime protocols in the Persian Gulf and the Gulf of Oman and to refrain from any adventurism and false and fake stories,” the statement said.

“They should be assured that the Revolutionary Guards navy and the powerful armed forces of the Islamic Republic of Iran sees the dangerous actions of foreigners in the region as a threat to national security and its red line and any error in calculation on their part will receive a decisive response.”

The U.S. military statement said the Iranian vessels approached six U.S. military ships conducting integration operations with Army helicopters in international waters.

At one point, the Iranian vessels came within 10 yards of the U.S. Coast Guard cutter Maui, the U.S. military said.

In its statement the Guards navy denied the U.S. military’s account of the incident and said the U.S. had acted unprofessionally.

While such incidents occurred occasionally a few years ago, they had stopped. But tensions between the two states spiked this year after the United States killed Qassem Soleimani, the head of Iran’s elite Quds Force, in a drone strike in Iraq.

Iran retaliated on Jan. 8 with a rocket attack on Iraq’s Ain al-Asad base, where U.S. forces were stationed. No U.S. troops were killed or faced immediate bodily injury, but more than 100 were later diagnosed with traumatic brain injury.