Two protesters were killed in India's Punjab state Monday in fierce rioting sparked by the shooting dead of a guru in fighting between rival Sikh communities in Austria, police said, AFP reported.
The two men were killed in separate incidents when police opened fire to disperse angry crowds who rioted in cities and towns across the northwestern state.
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 on Sunday as he addressed 200 worshippers.
Demonstrators in Punjab torched four train carriages in the city of Jalandhar, police said, despite a curfew imposed to halt the violence.
Curfews were also in place in the cities of Phagwara and Hoshiarpur, with more than 900 troops deployed to control the situation.
In Amritsar, Sikhism's holiest city and home to the Golden Temple, police fired tear gas to control crowds after protesters torched dozens of buses and smashed windows. 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.
Train services throughout the state were also severely disrupted.
Indian Prime Minister Manmohan Singh, himself a Sikh, said he was "deeply distressed" by the attack on the guru and issued an appeal for calm.
"Whatever the provocation, it is important to maintain peace and harmony among different sections of the people," he said in a statement.
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, or teacher, 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.
Leaders at the temple, which opened in 2005, have campaigned against the caste system, but their stance has angered other Sikhs in Austria.
Guru Nanak, who founded the Sikh religion in the early 16th century, denounced the Hindu hierarchy of castes and taught that all people were equal regardless of caste or gender.
Indian Foreign Minister S.M. Krishna blamed the attack on clan rivalry.
"Two groups of people owing allegiance to different families have set up confrontation amongst themselves and let the gurdwara (temple) be made the place where attacks and counter-attacks have taken place," he said.
Vienna police said that six Indian men who lived in Austria had been arrested over the assault.
But the Austrian authorities appeared to differ over whether the deadly clash had been planned or if was triggered by a sermon delivered at the temple.
"The sermon appears to have triggered the violence," Vienna's security and counter-terrorism bureau chief Werner Autericky told journalists. "The motive is not clear. We cannot yet talk of a planned action," he said.
His comments appeared to contradict those of Vienna police spokesman Michael Takacs, who said the attack had clearly been planned.
Four of the alleged attackers were 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, the army was out in force as protesters furious at the guru's death obstructed trains and erected road blocks on national highways.
The Sikh religious community has about 2,800 followers in Austria and 25 million worldwide, most of them in northern India.