Refugees from war-torn Yemen fleeing intense airstrikes are arriving in the Horn of Africa nation of Djibouti, aid agencies said Wednesday, warning of a possible large influx ahead.

While a total of 238 refugees from Yemen have registered in Djibouti in recent weeks, the UN refugee agency UNHCR said, preparations were being made for many more.

"UNHCR and the Djiboutian authorities are expecting a big influx, but the extent is still unclear at the moment," Frederic Van Hamme, from UNHCR Djibouti said.

The movement of refugees from Yemen to Djibouti and Somalia reverses a decades-old trend whereby Somalis have sought safety from decades of war in Yemen.

"The situation in Yemen is very violent and the people there are suffering," the International Committee of the Red Cross (ICRC) said Wednesday in a statement from Djibouti.

"The ICRC is scaling up its presence in Djibouti in anticipation of a possible increase in the number of people who may flee the southern regions of Yemen in search of safe haven from the fighting."

A sea channel only 30 kilometres (20 miles) wide at its narrowest point separates Djibouti and Yemen.

A refugee camp site is being set up in Markazi near the small northern port of Obock, Van Hamme added.

- Fierce ground fighting -

"Yemen is undergoing intense air strikes and fierce ground fighting nationwide," the ICRC added, noting that "air strikes continued in Sanaa, Taez, Ibb and Al Dhaleh over the last 24 hours," while in the key southern port of Aden "there have been sporadic clashes with use of tanks in many parts of the city".

ICRC is supporting the Djibouti Red Crescent Society "to help reconnect refugees with any family members they might have been separated from while fleeing the violence", it added.

More than 540 people have died and 1,700 been wounded since March 19 in Yemen, according to the World Health Organization.

Even as Yemenis begin to arrive in Somalia, the Arabian peninsula nation continues to host more than 238,000 Somali refugees, according to UNHCR.

UNHCR in Somalia has said it is "standing by" for more arrivals after the first Yemeni refugees arrived at the port of Berbera in northern Somaliland late last month, with Somalis also returning to their homeland.

Somalia's northern regions are impoverished and have suffered the knock-on effects of years of outright civil war further south, but are largely peaceful. In the southern parts of the Horn of Africa nation, African Union and Somali troops continue to battle Al-Qaeda-linked Shebab insurgents.