Ethiopian police have arrested 15 suspected militants allegedly trained by Islamist rebels in neighbouring Somalia and who were plotting attacks in Ethiopia, VOA reports.

The arrests were the latest in a crackdown on what senior officials say is a growing threat from militant Islam in Ethiopia, a Horn of Africa nation predominantly comprised of Orthodox Christians and a large minority of Muslims.

The would-be 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, the National Intelligence and Security Service (NISS) said.

Members of the group were recruited, trained and armed by Somalia's al Shabaab and their aim was to wage Jihad [holy war] and stage attacks inside the country, the NISS said.

Addis Ababa has sent troops to Somalia to help other African countries battling to crush al Shabaab's six-year insurgency.

The suspects, whose nationalities were not disclosed, were said to have crossed into Ethiopia from Somalia and Kenya.

Wednesday's TV report showed police displaying large amounts of arms including rifles and grenades, as well as black flags with Arabic inscriptions. The report said CDs and video tapes of "jihadist messages'' were also seized during the operation.