A taxi driver nearby said when Mr Dewji appeared, the auto parked inside flashed lights before the two white men alighted and seized him.
Mohammed Dewji, 43, who is said to have a fortune of $1.5bn (£1.1bn) and is the president of MeTL Group, which operates in about 10 countries across sectors ranging from agriculture to transport and food, was abducted as he entered a hotel gym.
The two kidnappers fired a gun and then they opened the gate, Dar es Salaam Regional Commissioner Paul Makonda said, adding that the two were believed to be foreign nationals.
Police have launched a manhunt into circumstances that led to the abduction of Mr Dewji who ranks as one of the richest Tanzanians at Colosseum Hotel as he walked into a gym.
Dewji is also the main shareholder in Tanzania's Simba FC football club.More news: US F-35 Jets are Grounded Following Crash
"Police are looking for suspects and have already made arrests", Mr Lazaro said.
Eye witnesses said four unidentified people arrived before the businessman and parked at the hotel.
Dar es Salaam special zone commander said security police around the country, including at airports and all exit points have been put on high alert in the hunt for the abductors.
Mr Dewji, locally known as Mo, is credited with turning his family business from a wholesale and retail enterprise into a pan-African conglomerate, reports the BBC's Athuman Mtulya from Dar es Salaam.
Dewji is also the first Tanzanian to join the Giving Pledge, a commitment by billionaires to help address society's most pressing problems by promising to give more than half their wealth to charity.