The family of a Tanzanian billionaire industrialist who was abducted last week offered $437 000 to anyone with new information that will lead to his rescue.

Three phone hotlines have been opened to gather information about the kidnapping of Mohammed Dewji, the 43-year-old owner of MeTL Group, a family spokesman told reporters Monday at the company’s offices in the commercial capital, Dar es Salaam. The spokesman, Azim Dewji, didn’t take further questions.

Twenty people have been arrested as police press a manhunt for Africa's youngest billionaire who was kidnapped in Dar es Salaam two days ago, a minister said Saturday.

Mohammed Dewji, who at 43 is Africa's youngest billionaire, was snatched by gunmen as he entered a hotel gym in Tanzania's economic capital on Thursday morning.

"Up until now, 20 people have been arrested," Interior Minister Kangi Lugola told reporters, without giving any detail on their identities. "Security forces are working day and night" to find him.

Officials have implicated the involvement of foreigners, saying he was taken by "whites".

Dewji is chief executive of the MeTL Group which operates in some 10 countries and has interests in agriculture, insurance, transport, logistics and the food industry.

According to Forbes, he is worth $1.5 billion (1.29 billion euros) and ranks 17th on the list of African billionaires.

Between 2005-2015, he served as a member of parliament and in 2013, he became the first Tanzanian to grace the cover of Forbes magazine. Two years later, he was named Forbes' Africa Person of the Year.

Dewji is also the main shareholder in Tanzania's Simba FC football club.