“The group was … preparing to attack hotels, religious festivities gathering places and public areas in Addis Ababa,” said the National Intelligence Security Services.
Ethiopia worked with neighbouring Djibouti to detain the suspects including their leader, Muhammed Abdulahi.
NISS did not specific the number of members detained, but said that they were arrested in the Ethiopian capital Addis Ababa, Oromia and Ethiopia’s Somali region.
Al Shabab has been fighting for years to topple Somalia’s central government, which the African Union-mandated peacekeeping force AMISOM helps to defend.
The militants have carried out numerous attacks in Somalia on military and civilian targets, and it has also conducted attacks abroad including in Kenya.
Al Shabab militants have targeted hotels before when at least 26 people, including several foreigners, were killed and 56 injured in a suicide bomb at the popular Medina hotel of Kismayo on July 13.