ALASAA, Libya: Exhausted, pregnant and weeping, Sudanese nurse Tafaul Omar sat under the scorching desert sun along with 14 other migrants who said they had been arrested by Tunisian authorities and dumped in the border area with Libya - a practice Tunisia denies.

The group of men and women from Sudan, Senegal, Ghana and Mali had walked for four hours before a Libyan border patrol that Reuters accompanied found them at the weekend and gave them water and food, Omar and the others said.

"It was just a horrible feeling to walk in the middle of nowhere," she said with sand caking her clothes, adding that she feared for her unborn baby after her ordeal in the desert.

Migrants, Libyan border guards and rights groups accuse Tunisia of expelling migrants across the frontier into a featureless wilderness far from towns or villages in the height of summer as part of a months-long crackdown.

Libya has reported finding bodies of migrants who died in the desert.

Tunisia's Interior Ministry denies dumping migrants in the desert and President Kais Saied has described the reports as misinformation aimed at discrediting the country.

"Tunisia rejects all accusations of expelling African immigrants," said Interior Ministry spokesperson Faker Bouzgaya, when asked by Reuters about the migrants' accounts.

Asked how those stranded in the desert had arrived there, he said "People who meet the conditions for legal entry into Tunisia will be allowed in," adding "Tunisia is not responsible for what happens outside its borders" without elaborating.

Bouzgaya pointed to work by Tunisia's Red Crescent to assist migrants at the border.

REMOTE AND DESOLATE

Omar, 26, said she and her husband Yaseen Adam had been living in Zarziz, a southern Tunisian town near the border with Libya, saving up to pay smugglers to take them to Italy. She said police arrested them last week and drove them to the border.

The couple fled their Khartoum home because of the warfare that suddenly broke out there in April with shellfire in their neighbourhood killing Omar's father, and travelled through Chad and Algeria before arriving in Tunisia, they said.

After the police arrested them along with other migrants, they beat the men, took the phones of everybody in their group and abandoned them in the desert, Omar, Adam and the others found by the Libyan patrol and the Reuters reporters said.

Reuters could not independently verify their accounts of what took place before they were found in the desert.

The U.N. migration agency IOM said about 300 individuals had been provided with food and medical assistance by it and other U.N. agencies at a Libyan government facility in Alasaa in Libya, near where Omar's group were found.

"The situation at the border is very complicated: it seems there are around 350 migrants still stranded in Ras Ijder", a coastal area about 35km (20 miles) from Alasaa, said Giacomo Terenzi of the IOM in Libya.

Last month the IOM and the U.N. refugee agency UNHCR said they were deeply concerned for the safety of hundreds of migrants, refugees and asylum seekers in Tunisia who had been removed to "remote and desolate" border areas or pushed across the frontier.

CRACKDOWN

Expulsions over the desert border were first reported in early July after confrontations between local people and migrants in the port city of Sfax, a main departure point for illicit voyages to Italy on small, flimsy boats.

Thousands of migrants who had been living in Tunisia have tried to leave for Europe this year after President Saied announced a crackdown on them in February, saying their presence was part of a plot to change Tunisia's demographic makeup.

That campaign, denounced by the African Union for what it called "racialised language", prompted a wave of reported attacks on migrants from sub-Saharan African countries.

Migration across North Africa and the Mediterranean to Europe has surged this year and shows little sign of slowing, with more departures - and deadly shipwrecks - reported on routes through and from Libya, Tunisia, Algeria and Morocco.

Despite the criticism directed at Tunisia's approach, the European Union last month said it would give the country more than 100 million euros to help combat people smuggling and improve border management.

Rights groups have also criticised the EU for its support of migration measures in Libya, where armed factions control migrant detention centres in which Amnesty International and Human Rights Watch have documented torture. Libya's government has denied there is torture at the centres.

Omar and her group said they had been given water and food by Libyan border guards, which come under Brigade 19 of the Tripoli government's Defence Ministry.

When the patrol found them, they were lying on the ground resting, their lips chapped and ashen, their heads covered with scarves against the sun and a strong sand-filled wind.

The border guards said they would be transferred to the government facility in Alassa. Terenzi said migrants it was working with there would not be sent to detention centres.

Kufi Mousa, 23, and his wife Blessing David, 20, were also in Omar's group. They reached Tunisia three months ago via Algeria, they said. Like Omar, David said she was pregnant. They had hoped to travel on to Europe but could not make enough money to do so.

"I'm frustrated. I've lost hope. I just want to return to Ghana. They expelled me and my wife and let us walk in the desert facing terrible conditions," Mousa said.