The arrests were the latest in a crackdown on what intelligence officials say is a growing threat from militant Islam in Ethiopia, a nation predominantly comprised of Orthodox Christians and a large minority of Muslims.
The suspected militants were caught following a 20-day sting operation while they plotted to set up cells in the eastern town of Harar and in Kemise in the northeast, Ethiopia's National Intelligence and Security Service said.
"Members of the group were recruited, trained and armed by Somalia's al Shabaab [militant group] and their aim was to wage Jihad and stage attacks inside the country," it said in a statement. The nationalities of those arrested were not revealed.
Addis Ababa has sent troops to Somalia to help other African countries battling a six-year insurgency by al Shabaab, which is allied to al Qaeda.
On Tuesday, an Ethiopian court convicted 10 other militants of preparing strikes on political and economic targets in Ethiopia with the group's help.