GENEVA: The United Nations launched an emergency appeal Tuesday for $1.7 billion to provide urgent humanitarian aid to people caught up in the Russian invasion of Ukraine and refugees fleeing the fighting.
The UN estimates that 12 million people inside Ukraine will need relief and protection, while it projected that more than four million Ukrainian refugees may need help in neighbouring countries in the coming months.
"This is the darkest hour for the people of Ukraine," UN humanitarian chief Martin Griffiths said in a statement.
"The crisis has turned very ugly, very fast. We must turn that initial shock and disbelief and uncertainty about the days to come into compassion and solidarity with the millions of ordinary Ukrainians who now need emergency relief and protection."
The UN's flash appeal wants $1.1 billion to assist six million people inside Ukraine for an initial three months.
Up to 40 percent of the funds will be distributed to people directly in cash.
The aid programme also includes food, water and sanitation, support for health care and education services, and shelter assistance to rebuild damaged homes.
The plan also aims to support the authorities in maintaining and setting up transit and reception centres for displaced people.
"We've all been watching the frightening scenes of fear and devastation in Ukraine," Griffiths said.
"Families with small children are hunkered down in basements and subway stations or running for their lives to the terrifying sound of explosions and wailing sirens. Casualty numbers are rising fast.
"We at the UN stand with the Ukrainians in their hour of need."
Around 677,000 refugees have fled Ukraine for safety in neighbouring countries, while around a million people are estimated to be internally displaced, the UN refugee agency, UNHCR, said Tuesday.
"We are looking at what could become Europe's largest refugee crisis this century," said UNHCR chief Filippo Grandi.
He said humanitarian aid could not solve the crisis.
"This is simply to try to bring some help to the people affected -- but the numbers that we are beginning to see are extremely worrying," he told a press conference in Geneva.
Grandi said the first wave of people fleeing across Ukraine's borders were likely to be people with cars, resources and some connections in other European countries.
But if Russia's military offensive continues and more urban centres are hit, people who are "more vulnerable in every respect" could start to flee.
"That is really what worries us more," he said.
An inter-agency refugee response plan is seeking a preliminary $550.6 million to help refugees in Poland, Moldova, Hungary, Romania, Slovakia and other countries in the region.
The appeal is to help provide shelter, emergency relief items, cash assistance and psycho-social support.
Six days into their invasion, Russian forces struck cities in eastern Ukraine and massed armoured vehicles and artillery near the capital Kyiv on Tuesday, as Western powers promised further sanctions to bring down Russia's economy.