With bowls of goulash, offers of free lodging and rides to Budapest, or just a hug and kind word, Hungarians have rushed to the Ukrainian border to help refugees fleeing the Russian invasion.

For Janos Molnar, one of the dozens of Hungarians waiting on Sunday at the Tiszabecs border-crossing with food and aid supplies, the support is a "moral duty".

"I have three empty rooms at home in my nearby town, these people have been through hell," the 50-year-old told AFP while holding a placard written in Ukrainian.

According to police data more than 70,000 refugees have streamed into Hungary from Ukraine since Thursday. Pulling their suitcases toward the throng of stalls with water and food packages, a weary group from conflict-torn Donetsk and Kharkiv in eastern Ukraine gratefully accepted Molnar's offer.

The invasion triggered a rapid response by ordinary Hungarians with citizens, church charities, and mayors of border towns springing into action.

"When we saw what was happening we set up a Facebook appeal for donations," said Zoltan Havasi, a bike courier who runs the "Budapest Bike Maffia" charity in the Hungarian capital.

Within hours thousands of people delivered canned food, mattresses, sanitary and baby products to a warehouse, said the 46-year-old.

"People wanted to actively help, not just send money," he said before setting off for the border from Budapest in a convoy of a dozen vans.

"There is more than is needed now, but a lot of it is non-perishable," the convoy's co-organiser Akos Toth told AFP as he unloaded the items in the border town of Zahony, part of a human chain of local volunteers.

"It will be useful if or when the situation in Ukraine escalates," said Toth, founder of a children's aid agency called "Age of Hope".

Van driver Attila Aszodi told AFP that he will carry refugees to Budapest on the return ride and "come back tomorrow if needed".

"I saw on the internet that they were looking for drivers with their own vehicles so I drove straight over," said the 44-year-old businessman.

"This is about humanity, anyone of us can suddenly become a refugee, as we saw this week in Ukraine," he said.

 According to Zahony mayor Laszlo Helmeczi around 5,000 people have arrived by train since Thursday, mostly women and children.

Helmeczi, 50, converted the town cultural centre into a makeshift refugee hostel, arranging 300 mattresses in rooms normally used for concerts and exhibitions.

The efforts echo a similar humanitarian response in 2015 when Middle Eastern and African refugees and migrants poured through Hungary at the peak of Europe's migration crisis.

Some were stranded for weeks at a train station in Budapest, dependent on aid brought by civil relief groups.

Unlike then the fiercely anti-migration Prime Minister Viktor Orban, who built a razor-wire fence in 2015 and border detention camps to keep out migrants, has now opened the EU member's door to Ukrainians.

A government decree last Friday exempted anyone arriving from Ukraine from Hungary's tough asylum laws, granting them temporary protection.

"Everyone fleeing Ukraine will find a friend in the Hungarian state," Orban said in an interview Sunday.