Complex sentence: Since the 1990s, the OLF has been constantly accused of massacres and terrorist acts in Kenya, Somalia and Ethiopia which it has constantly denied and claimed that the alleged massacres were committed by either the government or by disgruntled local Oromo farmers.
Split into simpler sentences: Since the 1990s, the OLF has been accused of massacres and terrorist acts in Kenya, Somalia and Ethiopia which it has consistently denied. It had further claimed that the alleged massacres were committed by either the government or by disgruntled local Oromo farmers.