The main airports in northern Europe were reopened Thursday afternoon after being briefly closed due to a new wave of volcanic ash, as disruptions continued in parts of Sweden and Finland.

The international Helsinki airport, as well as the airport in Sweden's second largest city Gothenburg were reopened.

All Norwegian airspace was again open, allowing airports in the second city of Bergen and its oil capital Stavanger to get back to business.

Helicopter flights to Norwegian offshore oil platforms also resumed.

Danish airspace was entirely open for a second straight day and Danish air traffic authorities also decided to open all airspace above Greenland, after closing the southern part on Tuesday.

But Danish air traffic authority Naviair said it could reintroduce flying restrictions if the concentration of volcanic ash in Danish skies increased, a spokeswoman told AFP.

Norway and Sweden had also reopened their airspaces on Wednesday, but eastern bound winds brought volcanic ash from Iceland back into Scandinavian skies Thursday, authorities said.

The airport in Sweden's third largest city Malmoe, in the far south, had remained open in the morning but was closed Thursday afternoon as the ash cloud shifted.

A number of smaller airports in Sweden and Finland remained closed the entire day.

The Helsinki-Vantaa airport was however opened and flag carrier Finnair said it expected its flight schedule to soon return to normal.

"Finnair can resume its traffic gradually as restrictions caused by the ash cloud have been removed from the Helsinki-Vantaa airport for the time being," Finnair said in a statement.

"Finnair will likely return to normal schedules during the end of the week," it added.

In the rest of Europe, most airspace was open for business Thursday with a normal quota of between 28,000 and 29,000 flights expected for the first time in a week, air traffic control coordinator Eurocontrol said.