DAR ES SALAAM, Tanzania

Hundreds of terrorists infiltrating from northern Mozambique killed at least 20 civilians in Tanzania’s southern Mtwara region, police and local media said on Thursday.

More than 300 Daesh/ISIS terrorists attacked civilians and damaged properties, forcing scores of people to abandon their homes.

A gruesome video circulating on social media showed the terrorists beheading a man believed to be Tanzanian.

One of them could be heard saying in Kiswahili language that they have nothing to do with the country’s general elections, set to be held on Oct. 28.

Police said the attackers entered Tanzania via the Ruvuma river and raided Kitaya village, located on the border with Mozambique’s troubled gas-rich Cabo Delgado province.

Without giving specific numbers, Simon Siro, Tanzania’s police chief, said some terrorists have been arrested and others ran away.

He said the suspects are being interrogated and a manhunt has been launched for those who fled back to Mozambique.

He vowed that the police and other security forces will defeat the “vicious network of terrorists, who are Tanzanians and Mozambicans.”

“If you kill Tanzanians, their blood cannot go in vain. We will do all we can to bring them to justice,” said Siro.

Violence in northern Mozambique has intensified over the course of this year, with terrorists attacking important military targets and even seizing key towns.

Attacks around Tanzania’s border with Mozambique have increased security risks for investors eyeing multibillion-dollar offshore gas projects.