Prague  -   A plane operated by a Norwegian low-cost airline made an emergency landing at Prague's Ruzyne international airport Wednesday after an alert indicated fire on board, officials said.

The Norwegian Air Shuttle Boeing landed in Prague just after 1400 local time, 21 minutes after taking off from the Czech capital for Oslo.

An alarm signaled fire in plane's auxiliary power unit, Czech Republic's Air Navigation Services spokesman Richard Klima said.

None of the 131 passengers was injured. Officials in Prague declined to say whether the power unit had been actually on fire.

The state-owned Ruzyne, which handled 12.4 million passengers in 2007, is the second largest international airport in central Europe after Vienna. It is served by 51 airlines, nearly a third low-cost. (dpa)