Washington: An Iranian warship attempted to seize unmanned surface vessels in the Red Sea belonging to the US Navy, marking the second incident in a week's time where Iran tried to capture a US vessel, 5th Fleet spokesman Tim Hawkins told Sputnik on Friday.

"We are aware of the claims. There was indeed an incident," Hawkins said .

Later on Friday, US Central Command Naval Forces issued a statement with details on the incident.

"The US Navy intercepted an Iranian warship that seized and detained two US unmanned surface vessels operated by US 5th Fleet in the Red Sea, Sept. 1, two days after Iran was unsuccessful in seizing a similar vessel in the Arabian Gulf," US Central Command Naval Forces said in a statement.

An Islamic Republic of Iran Navy ship seized two US Saildrone Explorer vessels operating in international waters before returning the vessels to the US Navy the next day, the statement said.

The vessels were unarmed and taking unclassified photos of the surrounding environment, posing no risk to naval traffic and having operated in the Red Sea for more than 200 consecutive days without incident, according to the statement.

The US Navy on Tuesday said it stopped an Iranian Revolutionary Guard Corps Navy ship from seizing an unmanned surface vessel in the Persian Gulf.

However, Pentagon Press Secretary Brig. Gen. Pat Ryder said on Wednesday that he did not know for certain whether Iran was aware the vessel belonged to the US or what sort of markings it may have had.