At least 140 civilians including many women and children in Ethiopia were massacred during a raid by South Sudanese assailants, authorities have claimed. The perpetrators reportedly raided Ethiopian region and returned to South Sudan.

The attack took place in Jakawa in Ethiopia's Gambela region in the bordering area between the two landlocked African nations.

Ethiopian government officials said their troops are on the hunt for the attackers. Local eyewitnesses have told Sudan Tribune that thousands of heavily armed men stormed more than 10 villages, which are mostly dominated by Nuer ethnic tribe. Most of the South Sudanese fighters are thought to be from South Sudan's Murle tribe – the group of people who are closely linked to another ethnic tribe Dinka, from which South Sudan President Salva Kiir hails.

A statement from the Ethiopian government said: "140 civilians died in the attack carried out by bandits that crossed from South Sudan. Ethiopian troops are pursuing the bandits inside South Sudan. 60 of the assailants have been killed so far."

Ethiopia's Communications Minister Getachew Reda said that dozens of tribal people have also been abducted by the assailants. The attack was one of the worst incidents in recent months, since the conflict broke out in South Sudan two years ago. The massacre has also fuelled fears that the fighting could spillover over the neighbouring African nations, which are already struggling to stabilise themselves, as more than 250,000 refugees from South Sudan are being sheltered in various provinces in bordering areas.

South Sudan's Information Minister Michael Makuei was cited as saying by the Wall Street Journal: "We don't condone such acts. We are ready to cooperate with our Ethiopian brothers to apprehend the perpetrators, but we remain a sovereign nation."

The two-year-long violence, primarily a tribal conflict between Dinka and Nuer ethnic groups, in oil-rich South Sudan has claimed more than 50,000 lives so far and forced up to 2.5 million people to flee their homes.