Libya's flood disaster, which killed thousands in the city of Derna, also displaced more than 43,000 people, according to the International Organization for Migration (IOM).
A tsunami-sized flash flood broke through two ageing river dams upstream from the coastal city after Storm Daniel lashed the area on 10 September.
It destroyed entire neighbourhoods, sweeping an untold thousands of people into the sea.
The official death toll stands at more than 3,300 but the eventual count is expected to be far higher, with international aid groups giving estimates of up to 10,000 people missing.
"An estimated 43,059 individuals have been displaced by the floods in northeastern Libya," the IOM said, adding that a "lack of water supply is reportedly driving many displaced out of Derna" to other areas.
"Urgent needs include food, drinking water and mental health and psychosocial support," it added.
Mobile and internet services have been restored after a two-day disruption, following protests on Monday that saw angry residents blame the authorities for the high death toll.
Officials had blamed the communications outage on "a rupture in the optical fibre" link to Derna, but some internet users and analysts claimed there had been a deliberate "blackout".
Tripoli-based Prime Minister Abdulhamid Dbeibah announced that communications had been restored in the east, in a social media post.
War-scarred Libya remains split between Mr Dbeibah's United Nations-backed and nominally interim government in the west, and another in the disaster-hit east backed by military strongman Khalifa Haftar.
The dams that were overwhelmed by the torrential rains earlier this month had developed cracks as far back as the 1990s, Libya's top prosecutor has said, as residents accused authorities of negligence.
Much of the country's infrastructure has fallen into disrepair in the chaos since a 2011 NATO-backed uprising toppled and killed dictator Muammar Gaddafi.
Mr Haftar's forces seized Derna in 2018, then a stronghold of radical Islamists, and with the reputation as a protest stronghold since Kadhafi's days.
The demonstrators had gathered on Monday outside Derna's grand mosque and shouted slogans against the parliament in eastern Libya and its leader Aguilah Saleh.
In a televised interview yesterday, Libya's prosecutor general Al-Seddik al-Sour vowed "rapid results" in the investigation into the cause of the tragedy.
He added that those suspected of corruption or negligence "have already been identified", without naming them.
Meanwhile, survivors in Derna face new threats.
The UN warned this week that disease outbreaks could bring "a second devastating crisis" to the flood-hit areas.
Local officials, aid agencies and the World Health Organization "are concerned about the risk of disease outbreak, particularly from contaminated water and the lack of sanitation", the UN said.
Libya's disease control centre has warned that mains water in the disaster zone is polluted and urged residents not to use it.
