But this week the vessel carried out a different kind of mission: transporting shell-shocked civilians from conflict-hit Sudan to safety on Saudi soil.

It was part of a broader evacuation effort that has given Saudi Arabia a central role in Sudan's crisis, putting the Gulf kingdom's regional clout on display for a global audience.

As of Monday, Saudi Arabia had welcomed more than 5,400 civilian evacuees, the vast majority of them foreigners representing 102 countries on six continents.

"I've been terribly impressed with all of their work to help evacuate people, to put their navy at the disposal of people fleeing," said Cameron Hudson of the Center for Strategic and International Studies.

"This is an opportunity to burnish their reputation a few hundred kilometres from Yemen, where some of their worst behaviour has played out," Hudson added, referring to the war in which a Saudi-led military coalition has killed and injured thousands of civilians in air strikes since 2015.

Some analysts warn, though, that the evacuations risk overshadowing the complex role Saudi Arabia and other outside powers have played in Sudan's turmoil, especially their support for the two generals at the heart of it.

The fighting -- which has killed hundreds and wounded thousands so far -- partly resulted from "gentle hand-holding" of army chief Abdel Fattah al-Burhan and paramilitary leader Mohamed Hamdan Daglo when the world should have insisted on real reform, said Kholood Khair, founder of the Khartoum-based think tank Confluence Advisory.

"This is a momentary reprieve for the international community to focus on evacuations as the main story, rather than how we got here," Khair said.

"It's as if the evacuation efforts are the only story."

- 'No frills' -

That's certainly the impression given these days by some Saudi media.

When state-run channels aren't filming new arrivals disembarking in the port city of Jeddah, often with a Saudi flag in hand, they're interviewing diplomats praising the Saudi navy's speedy mobilisation.

Riyadh seems intent on capturing the kind of goodwill conferred on Qatar two years ago when it welcomed tens of thousands of civilians fleeing the resurgent Taliban in Afghanistan, said Saudi analyst Aziz Alghashian.

The kingdom is also "projecting its influence to Saudi audiences", Alghashian added, aiming to counter local "frustration with the lack of efficient media efforts covering Saudi achievements and its role as an international player".

Not everyone has been fully won over.

Khair, of Confluence Advisory, last week found herself in Port Sudan along with thousands of others desperate for a way out.

She described a chaotic, heavily securitised process in which traumatised survivors wait hours, sometimes days, to learn if they'll be approved for a Red Sea crossing that can take up to 20 hours depending on the vessel.

"It's a no-frills evacuation experience which is, I guess, to be expected, but I think it's not commensurate to the ways in which the Saudis have propagandised this evacuation as if it is a humanitarian mission," said Khair, who eventually got a spot on a British flight instead.

Still, she credited the Saudis with being "the only ones on the surface who are taking any kind of responsibility by providing this safe route out, even if it is marred by politics".

- Projecting influence -

Defence ministry spokesman Colonel Turki al-Maliki said military assets would continue to be allocated to evacuations "as long as the Saudi embassy is receiving requests from the other embassies".

Saudi officials are meanwhile positioning the kingdom as a mediator, leveraging ties to both generals stemming partly from their involvement in Yemen's war.

An envoy of Burhan's met on Sunday with Saudi Foreign Minister Prince Faisal bin Farhan, and Saudi officials have requested an emergency meeting of the Organisation of Islamic Cooperation.

This aligns with a recent drive for regional peacemaking that has seen Saudi Arabia move to restore ties with Iran and Syria.

The politics behind Riyadh's engagement likely means little to its beneficiaries, including the 52 evacuees who boarded the HMS Al Diriyah on Sunday.

After being plied with dates and Arabic coffee, the men, women and children spread out on rugs and tried to sleep, battling seasickness as the corvette raced to Jeddah.

Nearing the port, a Saudi commander addressed the group, apologising that he couldn't have made the journey more comfortable by offering beds to everyone.

His final words prompted them to break into applause.

"Once you get to Jeddah, there will be hotels inshallah," he said. "You will forget all about this trip."