The most recent murder victim, whose body was discovered on Friday, was the third person to have been killed in this way since the beginning of the year.
The murders all took place in the Mbeya area, close to the borders with Malawi and Zambia.
People from those countries as well as from the Democratic Republic of Congo are reported to have visited villages near Mbeya to buy human skins and organs.
A human skin can fetch a price of up to $9,000.
Boy victim
Earlier this year, two people were arrested over the murder of an 11-year-old schoolboy, as they waited to meet a suspected client from Malawi.
Security forces in the area are introducing special measures to combat the gruesome trade, Tanzanian radio reported.
The new strategies would include "educating citizens to shun superstitious beliefs and practices", and police from neighbouring countries would also be involved in operations, the radio said.
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