Magufuli said the funds from abroad were channelled through a local bank, which he did not name.
"There are dubious transactions where some people have attempted to bring funds into Tanzania through money laundering means," Magufuli said on Monday in a speech at State House when announcing the government's decision to purchase all the cashew nuts from farmers after rejecting prices offered by traders.
"It's good to see that the Governor (of BoT) is on top of this. They wanted to bring 150 billion/- into the country by money laundering through one bank."
Magufuli urged the central bank and BoT Governor Prof Florens Luoga, who was present at State House, to continue to be vigilant against money laundering.
The president insisted that his government would continue to tackle corruption, saying illegal financial proceeds would not be tolerated.
Magufuli also revealed that he would send a list of corrupt members of the judiciary to the Chief Justice, Prof Ibrahim Juma, for further action.
"I will send you a list of corrupt judges...there are about four of them," Magufuli told the CJ, who was also present at State House.
What is money laundering?
According to the Financial Intelligence Unit (FIU) in the Ministry of Finance and Planning, money earned through criminal activities is said to be “dirty”.
For this reason, criminals whose main goal is to profit from their criminal acts, have to “cleanse” such money of its illicit origin. In order to enjoy their ill-gotten gains, criminals commonly seek to disguise the illegal source of their profits.
"Money laundering is the term applied to the act of concealing the origins of such money and releasing it undetected into legitimate business activities, the purpose being to prevent it from being tracked and confiscated by the government," the FIU said on its website.
Money laundering is most commonly associated with criminal activities such as drug trafficking, corruption, kidnapping, extortion, tax evasion, trafficking people and a range of other criminal activities.
The FIU was established under the Anti-Money Laundering Act of 2006 to combat money laundering and the financing of terrorism. It is responsible for receiving reports on suspicious transactions related to suspected money laundering and terrorist financing activities, analysing and disseminating intelligence to appropriate law enforcement agencies for investigation and further action.
"Money laundering can distort business decisions, increase the risk of bank failures, take control of economic policy away from the government, harm a country’s reputation and scare away honest investors," said the FIU.
"Unchecked use of the financial system for money laundering and terrorist financing has the potential of undermining individual financial institutions’ integrity and ultimately that of the entire financial system and hence lead to erosion of the International confidence to invest in the country."
Money laundering is a serious crime in Tanzania where suspects charged with the offence are not eligible for bail.