Tanzania authorities say over 300 armed men from Mozambique raided a village in Mtwara region of the country, killing a number of locals.
It is the first time the Tanzanian authorities have publicly acknowledged the presence militants from Mozambique in the country.
Northern Mozambique is in the grip of a militant Islamist insurgency that has claimed more than 1,500 lives.
Last week, it was widely reported that conflict had spilled into Tanzania, with a number of villagers killed and on Thursday, the head of Tanzania’s police acknowledged this.
Inspector General Simon Sirro said 300 “terrorists” attacked a village in Mtwara region.
He said that Tanzanians were among the attackers and added that they were arrested before they could flee back to Mozambique.
“We will continue to confront [the attackers] until we are able to trace their network,” he said in a statement.
The Tanzanian government had previously declined to comment on the incident.
The insurgency in Mozambique is now in its third year and the government in Maputo is struggling to contain it.