Clashes between rebel Tuareg groups and governmental forces in the Azawad region of northern Mali broke out in mid-January.
In the past three weeks, at least 10,000 people are reported to have crossed to Niger, 9,000 have found refuge in Mauritania and 3,000 in Burkina Faso, the UN High Commissioner for Refugees (UNHCR) said.
In Niger, about two-thirds of the refugees are in the town of Chinegodar and most of them are camping on an open site under makeshift shelters, according to the Office for the Coordination of Humanitarian Affairs.
OCHA spokeswoman Elisabeth Byrs said the agency was particularly concerned as Chinegodar has dwindling food supplies with only three tons of grain in reserve and the commercial supply from Menaka been interrupted for a week.
“Families’ food reserves are virtually exhausted,” said OCHA.
Algeria is bracing to accept a “massive” influx of Tuaregs fleeing the violence, the head of the Algerian Red Crescent Society said.
“We are in a waiting phase. We are preparing for a massive influx of Tuaregs from Mali,” Hadj Hamou Benzeghir told AFP.
He said “hundreds” were lodged with family and friends and added there was no immediate need for setting up refugee camps.
The Azawad National Liberation Movement (MNLA) and other Tuareg rebels launched a fresh offensive on January 17, the largest since 2009 by the rebels, whose ranks have been boosted by the recent return of men who fought in Libya for toppled leader Moamer Kadhafi.
The Mali army said it had killed about 20 Tuareg rebels on Friday and Saturday in the northern city of Timbuktu and taken a dozen prisoners.
Humanitarian agency Doctors of the World (Medecins du Monde) announced on Monday it was suspending its activities in northern Mali because of the “deteriorating security” in the country.