Two missiles hit an Iranian state-owned oil tanker as it headed to Syria on the Red Sea, the Iranian government has claimed.

Tehran did not attribute responsibility immediately but said two explosions 20 minutes apart on the Sabiti tanker, which caused oil to spill from two tanks, were not the result of an accident.

The boat was about 60 miles from the Saudi Arabian port city of Jeddah when it was hit. The scale of the damage did not appear extensive in photos published by Tehran news agencies.

The blasts prompted speculation that they were a reprisal by Gulf states for attacks attributed to Iran on Saudi oil assets in September.

Meanwhile, the Pentagon announced it was sending at least 1,000 additional troops to Saudi Arabia. It said the deployment meant that in the past month 3,000 troops had been sent to the kingdom or had their deployment extended.

US Patriot missile defences failed to deter a cruise missile and drone attack that severely damaged two Aramco facilities and shocked the Saudi government last month. US officials have since discussed with their Middle Eastern ally how to strengthen Saudi defences, and the Pentagon said Friday’s deployment would “assure and enhance the defence of Saudi Arabia”.

This week Donald Trump announced he was pulling troops from the Syrian border with Turkey and said he wanted to end America’s endless wars in the Middle East.

It appears some of the newly announced troops are being despatched to replace other American forces expected to depart the region in the coming weeks.

The US and the EU attributed the September attack to Iran, rejecting claims by Houthi rebels in Yemen that they were responsible. A full UN report on the incident has not yet been completed

An Iranian foreign ministry spokesman said: “Those behind the attack are responsible for the consequences of this dangerous adventure, including the dangerous environmental pollution caused. The details and factors behind this act will be investigated and will be announced after the results are reached.”

Suggestions that the oil company that owned the tanker was blaming Saudi Arabia at this stage were denied.

Friday’s incident, if confirmed as an attack, would be the first such incident targeting Iranian-owned shipping in the Gulf, though a state-owned tanker, Grace 1, was seized by British authorities off Gibraltar on the basis that it was breaching an EU oil embargo.

Iranian news agencies stressed that the Sabiti was stable, no crew had been injured and the leak was being brought under control.

Iranian ships routinely turn off their transponders to prevent tracking, but the Sabiti turned on its tracking devices late on Friday morning in the Red Sea, according to data from MarineTraffic.com.

The vessel last turned on its tracking devices in August, showing it near the Iranian port of Bandar Abbas.

Dryad Global, a firm specialising in oil shipping intelligence, said the vessel’s proximity to the port of Jeddah made it plausible that Saudi Arabia could have been involved, or at the very least that the incident was intended to create the perception of Saudi involvement.

But it added: “In terms of Saudi interests within the region, it remains unclear why Saudi would seek to target Iran in this manner. An attack of relatively low sophistication with limited and almost negligible strategic gain would be highly irregular and not serve any Saudi strategic narrative. Further still, it is highly unlikely that the Saudis would risk an ecological disaster in an area of strategic significance such as the Red Sea.”

Tension in the strait of Hormuz has been heightened for months as the US and Iran spar over Washington’s decision in 2018 to withdraw from the Iranian nuclear deal and impose worldwide sanctions on Iran including its oil exports.

Q&A Why is the Gulf of Oman so important for shipping oil? Show The strait of Hormuz, which provides passage from the Gulf of Oman to the open sea, is the most important gateway for oil exports in the world. With Iran on its northern shore, and the UAE and Oman on its southern shore, the US Energy Information Administration (EIA) calls it the world’s worst 'chokepoint' In 2016, 18.5m barrels of crude oil were transported each day through the strait of Hormuz, compared with 16m through the strait of Malacca, which runs between the Indonesian island of Sumatra, Malaysia and Thailand, connecting the Indian Ocean with the South China Sea. 5m barrels of crude oil are transported annually through the next largest chokepoint, the Suez canal. Phillip Inman

An attempt by the French president, Emmanuel Macron, at the UN general assembly in New York to engineer a meeting between the Iranian president, Hassan Rouhani, and Trump failed as the two sides could not reach agreement on the sequencing of the compromises the two sides would have to take. Since then, the Pakistani prime minister, Imran Khan, has stepped forward as a possible mediator between Iran and Saudi Arabia.

The perception was that neither Saudi Arabia nor the UAE, Iran’s two main Gulf rivals, were looking to escalate the crisis by undertaking a military response to the Aramco incident. It would be surprising if either Gulf state resorted to the kind of “plausible deniability” tactics allegedly deployed by Iran.

Israel is also deeply hostile to Iran but has confined most of its attacks to Iranian military sites in Syria.

The current round of attacks on oil shipping started on 12 May when four ships, including two Saudi oil tankers, were attacked in the Gulf just outside the strait of Hormuz, which is a major oil shipping route.

US and British officials blamed Iran, a charge Tehran denies. A further two tankers were hit on 13 June, and a week later Iran said it had shot down a US surveillance drone, an attack that nearly led to a major reprisal by the Trump administration.

Oil prices jumped 2% after reports of the tanker blasts on Friday, with crude futures rising by more than $1 (79p) a barrel.