Iran's Alborz warship has entered the Red Sea at a time of soaring tensions on the key shipping route amid the Israel-Hamas war and Houthi attacks on vessels.

Iranian state media did not give details of the Alborz's mission but said Iranian warships had been operating in open waters to secure shipping routes, combat piracy and carry out other tasks since 2009.

Yemen's Iran-backed Houthis have been targeting vessels in the Red Sea since November to show their support for the Palestinian Islamist group Hamas in its war with Israel.

In response, many major shipping companies have switched to the longer and more costly route around the Africa's Cape of Good Hope rather than pass through the Suez Canal, which handles about 12% of global trade.

The Alborz warship entered the Red Sea via the Bab al-Mandab Strait, IRGC-affiliated Tasnim news said, without saying when. There were unconfirmed reports on social media it arrived late on Saturday.

The Alvand class destroyer had been a part of the Iranian navy's 34th fleet, alongside the Bushehr support vessel, and patrolled the Gulf of Aden, the north of the Indian Ocean and the Bab Al-Mandab Strait as far back as 2015, according to Iran's state-run Press TV.

The US Fifth Fleet said it could not speak for the Iranian Navy or comment on the unconfirmed reports of the Iranian vessel's movements.

Houthi militants attacked a Maersk container vessel with missiles and small boats on Saturday and Sunday, prompting the company to pause all sailing through the Red Sea for 48 hours.

The head of Iran's Navy, Shahram Irani, was quoted in Iranian media on December 2 as saying that the Alborz was carrying out missions in the Red Sea.

Iran's Defense Minister Mohammad Reza Ashtiani said on December 14 in reference to the Red Sea that "nobody can make a move in a region where we have predominance".

(Report by Reuters)