Officials in Libya have said at least 150 people were killed in the flooding in Libya after storm Daniel swept the Mediterranean, lashing Turkey, Bulgaria, and Greece.

But Tamer Ramadan of the International Federation of Red Cross and Red Crescent Societies said the actual toll was likely many times higher.

"Our teams on the ground are still doing their assessment, (but) from what we see and from the news coming to us, the death toll is huge," he told reporters in Geneva via video link from Tunis.

"It might reach to the thousands."

"We don't have a definite number right now," he said, stressing though that the organisation had independent sources saying "the number of missing people is hitting 10,000 persons so far."

Speaking on the Libyan network Almasar, Oussama Hamad, prime minister of the east-based government, has reported "more than 2,000 dead and thousands missing" in the city of Derna alone, but no medical sources or emergency services have confirmed such figures.

But Ramadan said that judging from the figures he was seeing, "it's very likely that the number declared (by the eastern official) could be close to the correct number".

He said he hoped the IFRC would be able to provide a more precise toll of the disaster later Tuesday.

"The humanitarian needs are much more beyond the abilities of the Libyan Red Crescent and even the abilities of the government," Ramadan said.

"That's why the government in the east has issued an international appeal for support," he said, adding that IFRC was also preparing to launch an emergency appeal for funds towards the response.

On Tuesday, the Anadolu News Agency quoted a source in the Libyan Red Crescent saying at least 2,800 people have died in the flash floods across cities in eastern Libya so far.

'Epic proportions'
 

World Health Organization spokeswoman Margaret Harris meanwhile described the situation in Libya as "a calamity of epic proportions".

Experts have described storm Daniel -- which killed at least 27 people when it struck parts of Bulgaria, Greece, Turkey in recent days -- as "extreme in terms of the amount of water falling in a space of 24 hours".

In eastern Libya, the storm hit the coastal town of Jabal al-Akhdar especially hard, as well as Benghazi, where a curfew was declared and schools closed for several days.

The United Nations' World Meteorological Organization (WMO) meanwhile described how "entire neighbourhoods" in Derna had disappeared and their inhabitants been "swept away by water, after two ageing dams collapsed making the situation catastrophic and out of control".

Speaking on Libyan network Almasar, Oussama Hamad, prime minister of the east-based government, has reported "more than 2,000 dead and thousands missing" in the city of Derna alone.

Hamad's government -- which in war-battered Libya rivals a UN-brokered, internationally recognised transitional administration in Tripoli -- has declared Derna a "disaster area".

While no medical sources or emergency services have confirmed Hamad's figures, Ramadan said it appeared "very likely that the number declared (by the eastern official) could be close to the correct number".

He said he hoped the IFRC would be able to provide a more precise toll of the disaster later on Tuesday.

The UN's Organization for Migration meanwhile voiced concern about the impact the flooding may have had on the many already very vulnerable migrants in the country.

Egypt in mourning
 

Also on Tuesday, Egyptian President Abdel-Fattah El-Sisi declared a three-day mourning in the country in solidarity with the victims of humanitarian disasters in Libya and Morocco.

President El-Sisi also directed the Armed Forces to provide humanitarian aid, including relief teams, rescue equipment, and shelter camps, in cooperation and coordination with Libyan and Moroccan authorities.

Other world countries have also rushed to express solidarity with the Libyan people in the face of the catastrophe triggered by the storm.