The United Nations refugee agency says about 33,000 people have fled Ethiopia’s embattled Tigray region into neighbouring Sudan.

The United Nations High Commissioner for Refugees said Sudan is preparing to take in up to 200,000 in the next six months if necessary.

Axel Bisschop, the agency’s representative in Sudan, told reporters that “nobody at this stage can say exactly how many will come” but UN officials said fighting continues between Ethiopian government and Tigray regional government forces.

Some of the refugees are arriving with accounts of shelling or airplanes flying overhead, but Mr Bisschop said for now authorities are asking mainly “humanitarian questions” as they urgently seek to provide services.

The refugees are arriving in a very remote area, and humanitarians must create a crisis response virtually from zero even as up to 5,000 refugees continue to arrive every day.

Hameed Nuru, the Sudan country representative for the World Food Programme, said: “We have not heard specifics from the fighting, but what definitely is clear is that fighting is ongoing and it is sporadic, you never know where it’s going to happen. So it is this anticipation and not-knowing which is causing a lot more fear and causing people now to cross.”

He also noted reports that some fighters may have put down their arms and joined the flow of people crossing, which could add to tensions among those who fled.

The Unicef country representative in Sudan, Abdullah Fadil, said about 45% of the refugees are children under the age of 18.

He said: “This could unravel Ethiopia and also Sudan. Soon we will be overwhelmed … if this rate continues.”

While they said they saw no sign of cross-border fighting, they are trying to move the refugees away from the border just in case.

People left in a great hurry, the UN officials said, and most arrived in Sudan with nothing.

Mr Fadil said: “It’s a mix of medical doctors, professionals, bankers, to farmers. You could tell some people were actually well-off.”

Ethiopia’s government has been fighting the Tigray regional forces since a November 4 attack on a military base there. Each side regards the other as illegal, the result of a falling-out between Nobel Peace Prize-winning Prime Minister Abiy Ahmed and the Tigray leaders who once dominated the country’s ruling coalition.

With communications to the region severed, no-one knows how many people have been killed, and verifying either side’s claims is challenging.