The US military has evacuated American diplomats and their families from Khartoum, President Joe Biden has said.

"Today, on my orders, the United States military conducted an operation to extract US government personnel from Khartoum," he said in a statement.

Earlier Sudan's paramilitary army Rapid Support Forces (RSF) said six aircraft were used in Sunday's early morning mission, and that it had co-ordinated the evacuation with the US.

Several details are still unclear.

Exactly how many people were airlifted out of Sudan has not been confirmed. However before Saturday's operation, CBS News, the BBC's US partner, reported a plan to evacuate about 70 government workers.

Mr Biden confirmed the embassy in Khartoum is now closed: "We are temporarily suspending operations at the US embassy in Sudan."

He also thanked Djibouti, Ethiopia and Saudi Arabia, saying they had been "critical to the success of our operation".

The president praised the embassy staff's "courage and professionalism" and "the unmatched skill of our service members who successfully brought them to safety".

It is the second evacuation of foreign citizens since violence erupted in Sudan's capital last week.

On Saturday, more than 150 citizens, diplomats and international officials were evacuated by sea to the Saudi Arabian port of Jeddah. They were mostly citizens of Gulf countries, as well as Egypt, Pakistan and Canada.

Arabic news service Al Hadath reported that the six US aircraft landed in the embassy compound, and several Twitter users posted that they could hear helicopter activity over the US embassy, however the BBC has been unable to verify this.

Khartoum airport has been repeatedly targeted by shelling and gunfire, making evacuation flights from there impossible.

An unnamed US official told the Associated Press that President Biden had ordered the evacuation on Saturday after receiving a recommendation from his national security team, who saw no end to the fighting.

Mr Biden's statement said "I am receiving regular reports from my team on their ongoing work to assist Americans in Sudan, to the extent possible."

"We are also working closely with our allies and partners in this effort."

He condemned the "tragic violence" in Sudan, saying "it's unconscionable and it must stop".

"The belligerent parties must implement an immediate and unconditional ceasefire, allow unhindered humanitarian access, and respect the will of the people of Sudan."

The UK says it is considering ways to evacuate its staff. A hotline has been set up for those who need urgent help, and UK citizens in Sudan are being urged to tell the Foreign Office where they are.

Any UK evacuation is expected to be very limited and focus on diplomatic staff - not comparable to the mass evacuation from Afghanistan in 2021.

Meanwhile the Canadian government has told its citizens in Sudan to "shelter in a safe place".

Describing the security situation as "highly volatile", it told them to keep their phones charged, their doors and windows locked and "consider leaving the country if there's a safe means to do so".

Heavy fighting broke out in Khartoum on 15 April.

At the heart of it is a power struggle between forces loyal to Sudanese army chief Abdel Fatteh al-Burhan and a rival paramilitary faction, the Rapid Support Forces (RSF).

The near-constant shooting and bombardment in Khartoum and elsewhere has cut electricity and safe access to food and water for much of the population.

Several ceasefires that had seemingly been agreed by both sides were ignored, including a three-day pause to mark the Muslim holiday of Eid al-Fitr, which started on Friday.

UK Prime Minister Rishi Sunak chaired an emergency government Cobra meeting on Saturday to assess the Sudan crisis and more talks are expected on Sunday.

Foreign Secretary James Cleverly has cut short a Pacific tour and is returning to London.

Some UK nationals trapped in Sudan have voiced frustration and anxiety over the absence of an airlift.

Briton Iman Abu Garga, visiting Khartoum, said she had registered herself and her two children, as instructed, "and since then - nothing".

"We have no idea about timescale or timeframe. We have no idea what it's going to look like. Are we going to be airlifted out of Khartoum airport? Are we going to have to go by road? It's just utterly frustrating that there is no human contact whatsoever," she complained.

Another British citizen in Khartoum told the BBC she felt "completely abandoned" by the UK government, saying she had not been given "much information at all" about possible evacuation plans.