The six-seater Piper 32 aircraft was flying from Venice to Leipzig when it crashed and burned in a Slovenian forest, Slovenian news agency STA reported on Thursday, citing local police.

Ahead of impact, the 73-year-old pilot allegedly reported icing-related issues. The pilot was killed in the crash along with three passengers, including German millionaire Thomas Wagner.

The 38-year old internet entrepreneur founded his company Unister as a student in 2002. Currently, the firm boasts 1,200 employees and an yearly revenue of some 500 million euros ($555 million).

Unister is behind many popular German websites, including a matchmaking service Partnersuche.de, an online car market Auto.de, and a cheap flights portal Fluege.de. The company confirmed the CEO's death and vowed to "carry on our founder's legacy as best as we can."

In 2012, German authorities detained Wagner on suspicion of tax fraud. The late millionaire denied any wrongdoing and was soon released on bail. A trial was repeatedly delayed, with a Leipzig court still verifying the validity of the charges when the Thursday accident took place.

dj/bw (AFP, dpa)