Provocative clashes between Iranian ships and the U.S. Navy in the Persian Gulf have nearly doubled in the first half of 2016 to 19 from 10 during the same period last year, Fox News reports, citing new Pentagon data obtained from a U.S. defense official on condition of anonymity.

“In total, there have been 30 dangerous interactions with Iran so far this year, amounting to more dangerous dealings with the Iranians in eight months than all of last year. In 2015, 24 ‘unsafe interactions’ with the Iranians were recorded, according to the official,” reveals the news network.

The revelation comes after a U.S. Navy patrol ship in the Persian Gulf fired warning shots at three Iranian Revolutionary Guard Corps (IRGC) vessels that approached the American patrol ships USS Squall and USS Tempest at high speeds last Wednesday, in the second incident that week alone.

In May, a commander of the IRGC Navy threatened to “drown” U.S. warships if they pose a threat to Iran.

Fox News reports:

Dangerous confrontations between Iran and the U.S. Navy are becoming even more frequent than previously estimated, Fox News has learned. According to new data shared Monday with Fox News by a U.S. defense official, the number of provocative interactions between Iranian vessels and the U.S. Navy in the Persian Gulf nearly doubled in the first half of 2016 compared with the same time period a year ago.

“In the first half of 2016, we have seen nearly twice as many unprofessional and/or unsafe interactions when compared to the first half last year. That’s a disturbing rise and it has continued into the second half of the year,” declared the anonymous official.

In just the first six months of this year, Fox News explains, there were 19 “dangerous interactions with the Iranians,” which the U.S. military has deemed to be “unsafe and unprofessional.”

During the same period in 2015, “that number was 10, according to the official. The Iranian vessels acted as the aggressors every time, according to the U.S. Navy,” adds the news network.

The data shows that there have been 11 provocative incidents since July alone, a testament to the rise in Iranian aggression in the Persian Gulf and Strait of Hormuz.

Fox News notes:

There were four such encounters with Iran last week alone, including one that required warning shots from a U.S. Navy ship… This comes despite the highly touted nuclear accord, as well as a recent $1.7 billion U.S. payment to Tehran in January.

In January, vessels from Iran’s Revolutionary Guard Corps seized and humiliated 10 U.S. Navy sailors after their two ships drifted into Iranian waters. The American sailors were released the following day.

“If an American ship enters Iran’s maritime region, it will definitely get a warning. We will monitor them and, if they violate our waters, we will confront them,” declared Iranian Defense Minister Hossein Dehghan this week.

In response, Pentagon Press Secretary Peter Cook said, “[W]e certainly hope it doesn’t continue, because it serves no purpose other than to raise tensions in an important part of the world; and tensions that we don’t seek to have escalated.”