Opposition parties in Sri Lanka say they will mount a legal challenge to the detention of defeated presidential candidate Gen Sarath Fonseka. In a joint statement, the opposition parties said they feared the general would be killed in detention. The opposition has also called for protests over the arrest. The move comes after President Mahinda Rajapaksa dissolved parliament, paving the way for elections in April. Gen Fonseka was arrested on Monday, accused of working with anti-government forces and planning a coup and assassinations. He has denied the charges. His wife has visited him, but his supporters say they fear for his life.