All British nationals in Ethiopia have been told to leave “immediately” as it was announced that the country’s Nobel Peace Prize-winning prime minister has left to fight on the front line against rebels advancing on the capital.

“The conflict in Ethiopia is deteriorating quickly. In the coming days we may see the fighting move closer to Addis Ababa, which could severely limit options for British nationals to leave Ethiopia,” Vicky Ford, the minister for Africa, announced on Wednesday.

“Those who choose not to leave now should make preparations to shelter in a place of safety over the coming weeks. We cannot guarantee there will be options to leave Ethiopia in the future,” Ms Ford said, adding that interest-free loans were available to help British nationals who could not afford to buy a flight to return to the UK.

The news came as Haile Gebrselassie, the former Olympic champion runner, said he was ready to trade in his running shoes for army boots and head to the frontline to fight alongside Abiy Ahmed, the Ethiopian prime minister, according to state media.

Gebrselassie set 27 world records, won two Olympic gold medals in the men’s 10,000m, and bagged eight World Championship gold medals – indoor and outdoor – during his 25-year career.

“I am ready to do whatever is required of me, including going to the front line,” said the 48-year-old, who is regarded as a living legend in Ethiopia, akin to David Beckham in Britain.