EU transport ministers agreed on Monday to gradually lift flight restrictions from Tuesday, which have been imposed since a volcano in Iceland started spewing ash last week.

"From tomorrow morning we should see more planes flying," EU Transport Commissioner Siim Kallas told a press conference following a video conference with EU transport ministers.

The agreement will go into force at 0600 GMT on Tuesday, he said, adding "this is good news for Europe's stranded passengers, and good news for the airline industry and other sectors of the economy hard hit by this crisis."

He stressed that "there will be no compromise on safety. All the decisions must be based on scientific evidence and expert analysis."

The Eyjafjallajokull volcano in southeast Iceland began erupting on April 14 for the second time in a month from below the Eyjafjallajokull glacier, hurling a plume of ash 6 to 11 km into the atmosphere and causing the biggest travel chaos in years in Europe.

Volcanic ash contains tiny particles of glass and pulverized rock that can damage engines and airframes. So far, tens of thousands of flights have been grounded due to the volcanic ash cloud, causing billions of euros in loss.

Kallas told reporters that the ministers would hold further talks to discuss the economic impact of the crisis.

Under the agreement, European airspace is to be divided into three zones. The first zone with high density of the volcanic ash will not be open to any flight. The second zone with lower density will be opened up by national air traffic authorities. The third zone will cover airspace that is not affected by the volcanic ash.

The specific areas of the three zones are expected to be announced on Tuesday morning by the European Organization for the Safety of Air Navigation, or Eurocontrol.

Earlier on Monday, Eurocontrol said in a statement that 8,700 flights had taken place in European airspace, while on a normal Monday, 28,000 flights are expected.

"Air traffic control services are not being provided to civil aircraft in the major part of European airspace. This includes Belgium, Denmark, Estonia, Finland, Germany, Ireland, the Netherlands, northern Italy, Romania, Slovenia, Switzerland, parts of Ukraine and the UK," it said.

Eurocontrol acknowledged that in some of these areas the upper airspace has been made available, "depending on the observed and forecasted area of possible ash contamination. However, it is difficult to access this airspace as in most cases the surrounding area is not available for flights."

"Flights are taking place in southern and central Europe, including the Czech Republic, the Balkan area, Bulgaria, Hungary, southern Italy and France, Greece, Poland, Portugal, Slovenia, Spain, and Turkey, as well as parts of northern Europe (Norway and parts of Sweden)," it said.