(Reuters) – Explosions and fires rocked Sudan’s wartime capital Port Sudan on Tuesday, a witness said, part of a days-long drone assault that has torched the country’s biggest fuel depots and damaged its primary gateway for humanitarian aid in a major escalation.

The strikes included an unmanned aerial vehicle attack by Sudan’s paramilitary Rapid Support Forces (RSF) on Port Sudan facilities, targeting the container terminal, British maritime security firm Ambrey reported.

The strikes were the most intense since the attack on Port Sudan began on Sunday, in a conflict in which drones have played an increasing role, helping army advances earlier this year.

Massive columns of black smoke billowed from Sudan’s main strategic fuel caches near the port and airport on Tuesday, a witness in the city said, while strikes also hit an electricity substation and a hotel near the presidential residence.

The destruction of fuel facilities and damage to the airport and port risk intensifying Sudan’s humanitarian crisis, which the U.N. calls the world’s worst, by throttling aid deliveries by road and hitting power output and cooking gas supplies.

Port Sudan had enjoyed relative calm since the civil war between the army and the RSF suddenly erupted in April 2023. The Red Sea city became the base for the army-aligned government after the RSF swept through much of the capital, Khartoum, at the start of the conflict.

Hundreds of thousands of displaced people have also sought refuge in the city, where U.N. officials, diplomats and agencies have also set up headquarters, making it the main base for aid operations.

Inside Port Sudan, the attack on the electricity substation led to a power outage across the city while army units deployed around public buildings, the witness said.

Momentum in the conflict has repeatedly swung back and forth but neither side has looked likely to win outright. The drone strikes on Port Sudan open a new front, targeting the army’s main stronghold in eastern Sudan after it drove the RSF back westwards across much of central Sudan, including Khartoum, in March.

Military sources have blamed the paramilitary RSF for the attacks on Port Sudan since Sunday, though the group has not yet claimed any responsibility for the strikes.

The attacks came after a military source said the army had destroyed an aircraft and weapons depots in the RSF-controlled Nyala airport in Darfur, the main stronghold of the paramilitary group.

Hunger, Displacement

Sudan’s conflict has drawn in regional powers seeking to build influence in a country strategically positioned along much of the Red Sea coast and with borders opening onto North African, Central African and Horn of Africa countries.

The attacks have drawn condemnation from neighboring Egypt and Saudi Arabia, as well as expressions of concern from the United Nations.

Sudan’s army-aligned government has accused the United Arab Emirates of backing the RSF, accusations that U.N. experts have found credible and continued to investigate. The UAE has denied backing the RSF and the International Court of Justice on Monday said it could not rule in a case in which the government accused the UAE of fueling genocide.

The war, triggered by a dispute over a transition to civilian rule, has displaced over 12 million people and pushed half the population into acute hunger, according to the United Nations.

As the army pushed the RSF out of most of central Sudan, the paramilitary has made gains in more western and southern areas, while shifting tactics from ground incursions to drone attacks targeting power stations and other facilities deep in army-controlled territory.

The army has continued air strikes in the Darfur region, the RSF’s stronghold. The two forces continue to fight ground battles for control of al-Fashir, the capital of North Darfur state, and elsewhere as the battle lines in the war harden into distinct zones of control.

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(Writing by Nafisa Eltahir, Yomna Ehab and Angus McDowall; Editing by Aidan Lewis)