Female asylum seekers face physical assault and sexual harassment on their journeys through Europe, Amnesty International warned in a report on Monday, calling on governments to offer more protection.

The London-based human rights group interviewed 40 migrant women and girls in Germany and Norway who had travelled to Greece and then across the Balkans.

All those interviewed were from Iraq and Syria.

"Many reported that in almost all of the countries they passed through, they experienced physical abuse and financial exploitation, being groped or pressured to have sex by smugglers, security staff or other refugees," the report said.

It said women and girls travelling alone or accompanied only by their children felt particularly under threat in camps in Hungary, Croatia and Greece where they had to sleep alongside men and sometimes had to share bathroom and shower facilities with them.

"If this humanitarian crisis was unfolding anywhere else in the world, we would expect immediate practical steps to be taken to protect groups most at risk of abuse," said Tirana Hassan, Amnesty's crisis response director.

"At a minimum, this would include setting up single sex, well-lit toilet facilities and separate safe sleeping areas," she said.

One 22-year-old Iraqi woman told Amnesty that when she was in Germany, a uniformed security guard offered to give her some clothes in exchange for "spending time alone" with him.

"The best way to avoid abuses and exploitation by smugglers is for European governments to allow safe and legal routes from the outset," Hassan said.