AMRITSAR (AFP/Reuters) - Two protesters were killed in India on Monday as mobs went on the rampage after a guru was shot dead in fighting between rival Sikh communities in Austria, police said. The two men were killed in separate incidents when police opened fire to disperse angry crowds who gathered across the northern state of Punjab. They were protesting against the death of Sant Rama Nand, who was killed by fellow Sikhs in a temple in the Austrian capital of Vienna as he addressed 200 worshippers on Sunday. Rioters in Punjab torched four carriages of a train in the city of Jalandhar, police said, despite a curfew imposed to halt the violence. Authorities imposed a curfew on parts of the state and the army was put on standby after members mainly of the Dalit or untouchable community protested against the Vienna attack. The situation remains tense but under control, said senior superintendent of police RK Jaiswal, from Jalandhar town in Punjab where the violence was centred. In the Sikh holy city of Amritsar, police fired tear gas to control crowds after protesters torched dozens of buses. About 12 people were injured. One person was killed at Lambra village by the army bullet and another one was shot dead at Jalandhar by police in order to control the mob, a police officer who declined to be named told AFP. Indian Prime Minister Manmohan Singh said he was deeply distressed by the violence and issued an appeal for calm. Sant Rama Nand, 56, died and 16 other people were injured in Vienna during the temple attack, which was reportedly over a dispute about the role of castes in the Sikh religion. A second guru, Sant Niranjan Dass, 66, was among those wounded as Sikhs fought each other with guns and knives inside the temple. The two gurus, who belong to a group representing low-caste Sikhs, were visiting Vienna to meet worshippers at the temple. Leaders at the temple, which opened in 2005, have campaigned against the caste system that remains popular among some Sikhs. Their stance has angered other Sikhs in Austria who believe the correct traditions have been broken. Vienna police said Monday that six Indian men who lived in Austria were suspected of launching the pre-planned attack. Four of the alleged attackers are in a critical state in hospital, but the remaining two have been questioned, police said. In Jalandhar, the Indian city where many low-caste Sikhs live, protesters furious at the gurus death erected roadblocks on national highways to stop traffic and obstructed trains. Officers have been deployed at sensitive points to check any untoward incidents, said police superintendent R.K. Jaiswal. The Sikh religious community has about 2,800 followers in Austria and 25 million worldwide, most of them in northern India. Online adds: The Delhi-Lahore bus service 'Sada-e-Sarhad was stopped by authorities in Punjabs industrial city of Ludhiana Monday following large-scale violent protests by Dera Sachh Khand sect followers in the state, opposing the attack on sect leaders in the Austrian capital Vienna.