Three people have already been arrested for their role in the abduction of the richest man in Tanzania, police say.

Masked gunmen have kidnapped a man described as Africa’s youngest billionaire from a gymnasium in Tanzania’s economic capital Dar es Salaam, officials said.

Mohammed Dewji, 43, who heads the MeTL Group which operates in about 10 countries with interests from agriculture to insurance, transport, logistics and the food industry, was snatched as he entered the gym of a hotel in the city.

“Initial information indicates he was kidnapped by whites travelling in two vehicles,” Regional Governor Paul Makonda told journalists on Thursday.

“This kind of incident is new here,” he added.

Makonda said police have tightened security at all border points and airports to ensure that the two white men who were seen on surveillance video were not sneaking out of the East African nation.

Dar es Salaam police chief Lazaro Mambosasa told a press conference that the assailants had “shot into the air” before bustling Dewji into their car.

“Three people have already been arrested but we can’t divulge their identity for the moment,” he said.

Dewji, Tanzania’s richest man, is reportedly worth $1.5bn. He served as a member of parliament from 2005 to 2015.

In 2013, he became the first Tanzanian to grace the cover of Forbes magazine and was named Forbes Africa Person of the Year in 2015.

In 2016 he signed a pledge to donate at least half of his fortune to philanthropic causes, according to Forbes.

He is also the main shareholder in Tanzania’s Simba FC football club.