Dozens of villagers carried flowers and lit candles on Sunday at the site in rebel-held eastern Ukraine where flight MH17 crashed two years ago, killing all 298 people on board.

German and Swiss authorities have carried out raids seizing documents after learning a German private detective had investigated the MH17 air disaster, Dutch officials and media said on Tuesday.

Two tigers escaped from a big cat shelter near a small Dutch village on Saturday and remained free after a tranquiliser dart fired by police failed to take effect.

Dutch military police were on Wednesday investigating a major security alert triggered overnight at Amsterdam's busy international airport, with one man still in custody.