The Ogaden National Liberation Front (ONLF), an Ethiopian rebel group that is operating in eastern Ethiopia, denied that a weapons cache displayed by the government Woyanne regime belonged to them and accused the authorities of trying to tarnish their image.

On Saturday, state television showed what it said was more than four tonnes of explosives and thousands of bullets discovered by security forces after an ONLF leader surrendered and showed them the location of the arms dump.

The report said he had defected after refusing to work alongside neighbouring Somalia’s hardline al Shabaab insurgents — but on Monday the Ethiopian rebel group said that was a lie.

“Ethiopia Woyanne constantly parades fictitious ONLF deserters in front of the cameras … to get some semblance of credibility for its wishful claim of victory,” the ONLF said in a statement.

The ONLF is fighting for independence for the ethnically Somali Ogaden region, but it denies any links to al Shabaab, which Washington accuses of being al Qaeda’s proxy in Somalia.

Both the ONLF and Ethiopia’s government the Woyanne regime accuse each other of committing atrocities in the remote Ogaden region, which is believed to sit on top of significant mineral and oil deposits.

The ONLF has often warned foreign companies against working in the area, and in April 2007 its fighters killed 74 people at an oil exploration field run by a subsidiary of Sinopec, China’s biggest refiner and petrochemicals producer.

But the ONLF rebels said the latest allegations by the authorities in Addis Ababa were just an attempt to tarnish their reputation by linking them to Islamist insurgents in Somalia who are notorious for suicide bombings and assassinations.

“If Ethiopia Woyanne thinks that the countries it is trying to get more aid from have no intelligence services that are capable of knowing who is with whom in the Horn of Africa, it is in for a mighty shock,” the ONLF said in its statement.