German flag carrier Lufthansa said Tuesday it was diverting all Tokyo-bound flights to other Japanese cities at least until and including Sunday.
A spokesman stopped short of saying the measure had been taken because of fears of radioactivity however, telling AFP the move was "for different reasons."
The flights are being diverted to Nagoya and Osaka, which are located several hundred kilometres west of Tokyo and which are able to provide more stable ground conditions and connections at present, the spokesman said.
He added that Lufthansa continued to preventively check flights from Japan for radioactivity but has not found any traces to date.
Japan's nuclear crisis worsened on Tuesday following another explosion at the Fukushima Daiichi plant northeast of Tokyo, which was damaged Friday during a 9.0-magnitude earthquake and subsequent tsunami.
The official death toll has topped 2,400 people, police said on Tuesday.
According to the head of France's Nuclear Safety Authority (ASN), the concrete casing around the plant's No. 2 reactor, which is designed to contain radioactive debris, is "no longer sealed."
The accident now rates six on a seven-point international scale of gravity for nuclear accidents, ASN head Andre-Claude Lacoste told a press conference in Paris.
The 1979 accident at Three Mile Island in Pennsylvania rates five on an international scale of zero to seven, while the world's worst nuclear accident in Chernobyl, Ukraine, is put at seven, the highest.