Foreign ministry spokeswoman Mindi Kasiga told state television that the 21 Tanzanians and three Kenyans had been driving trucks belonging to two companies registered in Tanzania.
"They were kidnapped by Mai-Mai fighters on June 29 in Lulimba, in South Kivu province, while they were on their way to the Namoya gold mine in Maniema province," she said.
"According to information coming from the Tanzanian embassy in the Democratic Republic of Congo, the Mai-Mai rebels attacked the convoy which was being escorted by soldiers from the Congolese army."
Tanzania has asked the DRC government "to take into account the presence of these truckers as they carry out their operation against the rebels."
The eastern DR Congo has been rocked by more than 20 years of armed conflict among both domestic and foreign armed groups, fuelled by struggle for control of lucrative mineral resources as well as ethnic and property disputes.