ADDIS ABABA - Gunmen ambushed a bus carrying dozens of people in western Ethiopia near the Sudanese border, killing nine and wounding six others, state-run media said on Wednesday.

There was no claim of responsibility and no group was blamed for the attack, but Ethiopia says it has thwarted several plots in recent years by Ethiopian insurgents as well as Somali al-Qaida-linked al Shabaab Islamist militants.

A handful of rebel groups are waging low-level separatist insurgencies in Ethiopia, while Ethiopian troops are part of an offensive against al Shabaab in neighboring Somalia.

The bus ambush on Tuesday evening - near the $4 billion-Grand Renaissance Dam - was the second attack on public transportation in the Benishangul Gumuz region in five months. Four people were killed by a bomb on a minibus in November.

"The bus was targeted while travelling 100 kilometres (62 miles) south of (regional capital) Assosa," a report on state-owned Ethiopian Television said.

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