WASHINGTON, Aug 7 (Aljazeera) - More than 3,000 US military personnel have arrived in the Red Sea on board two warships, part of a beefed-up response from the United States after alleged seizures of several civilian ships by Iran, the US Navy said.

The US sailors and marines entered the Red Sea on Sunday after transiting through the Suez Canal in a preannounced deployment, the US Fifth Fleet said in a statement on Monday.

The deployment adds to a growing US military buildup in tense Gulf waterways vital to the global oil trade and led Tehran on Monday to accuse Washington of inflaming regional instability.

The US military says Iran has either seized or attempted to take control of nearly 20 internationally-flagged ships in the region over the past two years.

They arrived on board the USS Bataan and USS Carter Hall warships, providing “greater flexibility and maritime capability” to the Fifth Fleet, the statement from the Bahrain-based command added.

The deployment adds to efforts “to deter destabilising activity and de-escalate regional tensions caused by Iran’s harassment and seizures of merchant vessels,” Fifth Fleet spokesperson Commander Tim Hawkins told the AFP news agency.

USS Bataan is an amphibious assault ship that can carry fixed-wing and rotary aircraft as well as landing craft. The USS Carter Hall, a dock landing ship, transports Marines and their gear and lands them ashore.

In a Monday press conference, Iran’s foreign ministry spokesman Nasser Kanani said US deployments are only serving Washington’s interests.

“The US government’s military presence in the region has never created security. Their interests in this region have always compelled them to fuel instability and insecurity,” he told reporters.

“We are deeply convinced that the countries of the Persian Gulf are capable of ensuring their own security.”

The latest deployment comes after Washington said its forces blocked two attempts by Iran to seize commercial tankers in international waters off Oman on July 5.

The maritime services in Iran said one of the two tankers, the Bahamian-flagged Richmond Voyager, had collided with an Iranian vessel, seriously injuring five crew members, according to state news agency IRNA.

In April and early May, Iran seized two oil tankers within a week in regional waters.

Those incidents came after Israel and the United States blamed Iran in November for what they said was a drone strike against a tanker operated by an Israeli-owned firm carrying gas oil off the coast of Oman.

The US announced last month that it would deploy a destroyer, F-35 and F-16 warplanes, along with the Amphibious Readiness Group and a Marine Expeditionary Unit, to the Middle East to deter Iran from seizing ships in the Gulf.

Last week, the US military said it was considering putting armed personnel on commercial ships travelling through the Strait of Hormuz to stop Iran from harassing vessels, according to the Associated Press.

Tehran responded on Saturday by saying it was equipping its Revolutionary Guard’s navy with drones and 1,000km (621-mile) range missiles.