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Input: Tensions escalated Wednesday over the arrest of Sri Lanka's former army chief  Sarath Fonseka  with violent clashes outside the Supreme Court  where his wife petitioned for his immediate release.
 Opposition parties who backed Fonseka in his failed challenge to President Mahinda Rajapakse in January elections also demanded his release and said they feared for his safety in military custody.
 Fonseka was arrested by troops at his office in Colombo on Monday night and  according to the defence ministry  will be court-martialled on charges of conspiring against the government.
 Anti-riot police used tear gas and water cannon Wednesday to break up a clash between thousands of Fonseka supporters and ruling party activists outside the capital's Superior Courts complex.
 As order was restored  Fonseka's wife arrived to file a petition for her husband's release. Supreme Court officials said a hearing had been fixed for Friday.
 Opposition lawmaker Karu Jayasuriya said the combined opposition was seeking the support of the influential Buddhist clergy in pressuring the government to free Fonseka and curb a crackdown on dissidents and rival politicians.
 "We are speaking to all religious leaders and will have a series of religious events to seek the release of General Fonseka from custody and ensure more democratic freedoms " Jayasuriya said.
 Sri Lanka's former peace facilitator  Norway  joined the United Nations  France and the United States in expressing concern over Fonseka's arrest  saying it risked impeding progress towards "lasting political stability".
 Earlier this month  Rajapakse sacked a dozen senior military officers in an unprecedented purge. The defence ministry said the officers were a threat to national security. Party workers from Fonseka's office were also arrested.
 The Sri Lankan government is also concerned about Fonseka's apparent willingness to testify at any probe into alleged war crimes committed by Sri Lankan troops last year in the final stages of the conflict with Tiger rebels.
 "I am not prepared to protect anyone  if they have committed war crimes " Fonseka said before his arrest.

Violent clashes over arrest of Sri Lanka ex-army chief