Iran threatened to shoot down two US Navy surveillance aircraft flying close to Iranian territory in the Persian Gulf over the weekend, the latest in a series of recent provocations between Iran and the US military in the region, three US defense officials with knowledge of the incident told Fox News.

On Sept. 10, a Navy P-8 Poseidon with a crew of nine and an EP-3 Eries with a crew of roughly 24, were flying a reconnaissance mission 13 miles off the coast of Iran, through the Persian Gulf, Strait of Hormuz and Gulf of Oman, according to officials who call the boundary Iran’s “black line.”

Iran’s territorial waters—like all nations--extend 12 miles into the sea, according to international maritime law.

At some point during the flight, the Iranian military warned the two aircraft to change course or risk getting shot down.

The US military planes ignored the warning and continued flying in international airspace, although close to Iranian territory, the officials told Fox.

“We wanted to test the Iranian reaction,” one US official told Fox News when asked why the US jets were flying close to Iran.

“It’s one thing to tell someone to get off your lawn, but we weren’t on their lawn,” the official continued. “Anytime you threaten to shoot someone down, it’s not considered professional.”

The official said the Iranian behavior was characterized as “unprofessional.” Another official said the incident was not considered “unsafe” because there were no Iranian missile launchers in the area, according to the latest intelligence reports.

The latest incident between the US military and Iran is just the latest in a series of confrontations in region.

Last month, Iranian fast-boats harassed US Navy warships in the Persian Gulf on at least five occasions. One incident resulting in three warning shots being fired from a US Navy coastal patrol craft, when an Iranian vessel ignored repeated radio calls to change course. On another occasion, an Iranian boat stopped 100 yards in front of a US Navy ship forcing it to take evasive maneuvers.

Over the weekend, a senior Iranian military commander dismissed claims that his vessels had harassed US Navy ships in the Persian Gulf saying his nation acted in accordance with internationally recognized maritime law.

"Iranian boats continue to act based on defined standards and are well aware of the international laws and regulations, so the claims are not only untrue, but stem from their fear of the power of Iran's soldiers," said Brigadier General Masoud Jazayeri, deputy chief of staff of Iran's armed forces, according to state news agency IRNA and reported by AFP.

Dangerous interactions at sea between Iran and the US Navy have doubled in the first half of 2016 compared to the same time last year, Fox News first reported last month.

On Aug. 30, the head of US forces in the Middle East was asked to explain Iran’s perceived aggressiveness.

“This is principally the regime leadership trying to exert their influence and authority in the region. And they are trying to do it in provocative ways,” said Gen. Joe Votel, commander of US Central Command at a Pentagon press briefing.

In July, days after the one-year anniversary of the nuclear agreement, Iran attempted at least their fourth ballistic missile test in violation of a UN Security Council resolution tied to the nuclear agreement.

In January, Iran took 10 US Navy sailors captive after their two patrol boats traveled into Iranian waters before releasing them 16 hours later.

In December, an Iranian missile boat fired several unguided rockets close to a US Navy aircraft carrier transiting the Strait of Hormuz.