Mr Nyagali is a member of the main opposition Chadema party, and a fierce critic of President John Magufuli.
Leading Tanzanian opposition activist Mdude Nyagali, who was abducted on Saturday by masked gunmen, has been found dumped in a bush near a village in the south-western Mbeya region, local media reports say.
He appeared to have been tortured, looked weak, and had difficulty speaking, residents from Makwenje village are quoted as saying.
He was taken to hospital for treatment.
Mr Nyagali is a member of the main opposition Chadema party, and a fierce critic of President John Magufuli.
Chadema accused police of abducting him from his office on Saturday. Police denied the allegation.