The UN Stabilization Mission in DR Congo (MONUSCO) "Is currently carrying out enquiries concerning several acts of exploitation and abuse implicating members of our Tanzanian contingent" in the eastern province of North Kivu, said Maman Sambo Sidikou, the UN's special representative in the country.
Sidikou vowed action against Tanzanian peacekeepers found guilty of sexual abuses in Congo. He said that sanctions may be imposed after investigations by the UN and Tanzanian government.
Under UN rules, the responsibility for investigating and prosecuting peacekeeper sexual abuse lies with the countries that contribute the troops and police to the peace missions.
The Tanzanian troops are part of the UN mission's elite intervention brigade deployed at Mavivi, a village near Beni, since September 2015.
A UN team was sent to the area last month on a fact-finding mission.
The United Nations has been rocked by a wave of allegations that its peacekeepers sexually abused civilians in DR Congo and the Central African Republic.
"Tanzania... has sent a team of investigators and we are carrying out a joint enquiry," Sidikou told reporters in Kinshasa.
So far 18 cases of sexual abuse have been reported and eight of the victims were minors, said Sidikou. Some of the women have since given birth.
Those cases involved a South African, a Malawian and 16 Tanzanian soldiers.
Eleven of the cases concern UN troops on an earlier tour of duty up to July 2015.
Sidikou described the allegations as "shocking" and shameful to the United Nations, its force and those involved.
He said he hoped those guilty would be punished swiftly and their victims get medical and psychological help, "including the children, who must not be forgotten".
The UN peacekeeping mission in Congo, initially established during a civil war that lasted from 1998-2003, is the world's largest, with around 20,000 uniformed personnel.
The United Nations last month reported a "deeply concerning" increase in allegations of sex abuse by its peacekeepers, with 69 claims last year against troops from 21 countries.
Most of the allegations involved troops and police from African countries: Cameroon, Congo, Benin, Burkina Faso, Burundi, Gabon, Ghana, Madagascar, Niger, Nigeria, Rwanda, Senegal, Togo, and Tanzania.