Ethiopian troops have crossed into South Sudan in search of more than 100 abducted children who were kidnapped and spirited across the border in a surprise attack that also killed 208 people.

The attackers, who were armed with machine guns, killed anyone who tried to stop them from taking the children, including women, according to witnesses. They also took more than 2,000 livestock.

Estimates of the number of children snatched ranged from 102 to 125.

Those attacked were from the Nuer tribe, a community that has often been in conflict with the Murle.

Many survivors and witnesses to the attack says that the men had Murle tribal markings.

The Murle, a tribe from South Sudan based in the eastern Jonglei region near the Ethiopian border, often stage raids to steal cattle and abduct children but very rarely on such a large or deadly scale.

Ethiopia hosts more than 200,000 South Sudanese refugees who fled after war broke out in their country in December 2013.

After winning independence from Sudan in 2011, South Sudan descended into war two years later, setting off a cycle of retaliatory killings that have split the country along ethnic lines.

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