"We resumed flight operations shortly after noon. The first aircraft are currently being de-iced," a Berlin Brandenburg Airport spokeswoman told AFP.

Passengers should nevertheless expect "significant delays and flight cancellations" after "freezing rain fell again overnight", she added.

Only about a quarter of Thursday's flights were able to take off or land before the airport was shut that evening.

No sooner had the runways been cleared than more freezing rains made them slippery again, the spokeswoman said.

"We are doing everything we can," she added.

Bus services in many Berlin districts were also suspended late on Thursday, and transport in the northeastern states of Brandenburg and Mecklenburg-Western Pomerania were also severely disrupted.

Conditions on Berlin's roads remain "difficult" after days of freezing temperatures, city authorities said.

Conditions were expected to improve, with ice and slip warnings from Berlin to the Baltic Sea downgraded from red to orange.