BERLIN ? Germany closed Friday all its airports because of a cloud of volcanic ash from Iceland as Europe's biggest airline Lufthansa announced it had cancelled all flights in the country until Saturday.

German air navigation services provider DFS said Munich airport, Germany's second hub after Frankfurt, closed at 1800 GMT. The southern city's airport had been the last among Germany's 16 international airports to remain open.

Frankfurt, Europe's third busiest after London and Paris with up to 1,400 arrivals and departures a day, had halted all air traffic on Friday morning.

Airports in northern Germany including Berlin's Tegel and Schoenefeld, as well as Hamburg, Hanover and Bremen had closed earlier.

The other airports affected are Stuttgart, Nuremberg, Leipzig, Dresden, Erfurt, Cologne-Bonn, Duesseldorf, Muenster-Osnabrueck and Saarbruecken.

German airline Lufthansa announced separately it had cancelled all flights arriving and departing from German airports until midday Saturday.

"Lufthansa is canceling all its scheduled flights until Saturday, April 17 12:00 (1000 GMT) departing from and arriving at German airports," the German group said in its website.

"The concerned passengers are asked not to go to the airport," it added.

German Chancellor Angela Merkel has been unable to return home from a week-long US visit, with her plane redirected to Lisbon. Merkel traveled with an official delegation and reporters on board.

Her return flight to Berlin may not take off until Saturday midday "at the earliest" due to the required break accorded to the flight crew.

Meanwhile Defense Minister Karl-Theodor zu Guttenberg was waylaid en route home from Afghanistan, along with five soldiers injured in a Taliban attack that killed four of their comrades Thursday, a spokesman said.

After flying to a German airbase in neighboring Uzbekistan, they were redirected to Istanbul, where they were to land later Friday.

The troops were to be taken to a hospital there for further treatment before returning home "as soon as possible", the spokesman said. Guttenberg was to stay overnight in Istanbul.

Millions of passengers were stranded worldwide Friday after the volcanic ash from Iceland swept across Europe, grounding 16,000 flights according to Europe's air traffic control centre in the biggest air travel shutdown since World War II.