NEW DELHI, India (CNN) -- Three weeks after an apparent misunderstanding sparked a confrontation, deadly Hindu-Christian riots continue unabated in the remote east Indian state of Orissa.



Police officers chase away a protester in Mangalore, India, Monday.



By Tuesday, about 20 deaths had been reported, said Praveen Kumar, the superintendent of police in the worst-affected Kandhamal district.



The latest casualty is a police officer who died after an armed mob of about 400 to 500 mostly Hindus torched a police station in the district on Monday, Orissa state police said.



Orissa's Director General of Police G.C. Nanda the policeman died when the mob opened fire at officers fleeing the burning building.



The attack, he said, may have been in retaliation for arrests that police made in the ongoing communal fighting.  Watch more about the riots in India »



The attack came two days after police fired on a crowd to prevent it from attacking Christian residents. Between three and six people died in the shooting, CNN's sister network CNN-IBN reported.



The violence spread to southern India over the weekend when vandals attacked 14 churches in an hour in the state of Karnataka Sunday, the network said.



The Christian community in the Karnataka -- numbering about 2.5 million -- said right-wing Hindus are targeting them for opposing the violence in Orissa.



By Tuesday, police had arrested about 140 people in connection with the riots, said Karnataka's Inspector General of Police A.M. Prasad.



Sixty of them -- all Hindus -- were arrested for the church attacks, Prasad said. The rest, mostly Christians, were charged with disturbing the peace, he said.



Orissa has historically been a tinderbox of Hindu-Christian tensions.



Some Hindu groups view the work of Christian missionaries in the state with suspicion. They accuse missionaries of bribing or forcing Hindus into converting.



The seeds for the current conflict were planted on August 23, when Hindu leader, Laxmananda Saraswati, and four others were killed in Kandhamal after 20 to 30 gunmen barged into a Hindu school and began shooting, the Orissa chief minister's office said.



The authorities have not determined who killed Saraswati, but after the incident they detained five people who are Christians, said Sukanta Panda, spokesman for the chief minister.



The government says the killings may have been the work of Maoist rebels -- investigators have many unanswered questions -- but some hardline Hindus blamed a Christian minority.



They took to the streets in anger, rampaging through predominantly Christian neighborhoods, ransacking shops and torching houses.



They chopped down trees to block roads, making it difficult for police to reach trouble spots. A Christian orphanage was set on fire. A 20-year-old woman, who was teaching children inside, burned to death.



Christian residents fought back, and the clashes spread. Authorities imposed a night curfew in many towns and deployed state and federal forces in the troubled areas, Kumar -- the police superintendent -- said.



Both sides said the violence has left Christian churches and Hindu temples razed to the ground.



This is not the first time the simmering anger has boiled over in the state with deadly consequences. In 1999, a Hindu mob burned to death an Australian missionary, Graham Staines, and his two children while they slept inside their car.



And last Christmas, clashing groups killed four people and burned several churches in the same Orissa district -- Kandhamal.



Maoist rebels, who claim to be fighting for the poor and the dispossessed, have been battling the Indian government in an insurgency that has resulted in thousands of casualties since the late 1960s.



Some Christians accept the Maoist theory, saying the rebels have also struck against hard-line Hindus because they associate them as being closely aligned with the government.



But Hindu groups insists that Christians were behind Saraswati's death.



Unlike Orissa, Karnataka has until now been spared the large-scale clash between Christians and Hindus.



But now, many in the Christian community fear their calm and prosperous state may become another battleground between the two religions, CNN-IBN said.



CNN's Harmeet Singh contributed to
What state was a tinderbox of Hindu-Christian tensions? What was the latest casualty? Where has violence spread? Who died after a Hindu mob torched a police station? who was the latest casualty? What state of India violence spread? WHen did the attack happen? What did the police fire upon?
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question: What state was a tinderbox of Hindu-Christian tensions?, answer: Orissa. | question: What was the latest casualty?, answer: is a police officer | question: Where has violence spread?, answer: southern India | question: Who died after a Hindu mob torched a police station?, answer: officer | question: who was the latest casualty?, answer: police officer | question: What state of India violence spread?, answer: Orissa. | question: WHen did the attack happen?, answer: Monday, | question: What did the police fire upon?, answer: a crowd