A Sikh preacher died Monday after being wounded in an attack on his temple by a group of fundamentalist Sikhs armed with knives and a handgun, police said. India's prime minister appealed for calm as riots protesting the deadly shooting spread to several northern Indian cities.

Witnesses said the Vienna temple attended by lower-caste Sikhs had been attacked by Sikhs from a higher caste who accused one or both of the preachers of being disrespectful of the religion's Holy Book.

The attack set off a brawl that wounded 16. It was not clear whether some of the weapons used were kirpans — ceremonial daggers that may legally be worn by Sikhs in Austria.

Two preachers — identified by Indian diplomats as Niranjan Das and Sant Rama Nand — underwent operations for gunshot wounds, but Nand died early Monday, according to a police official who declined to identify himself on the telephone, in line with Austrian custom.

Hundreds in India defied a curfew and army patrols, attacking police stations and torching the car of a senior officer and several trains. In two places police opened fire on mobs, wounding at least four people, said senior police officer Khubi Ram.

The violence in Indian centered on the north Indian town of city of Jalandhar, a stronghold of the Dera Sach Khand, a Sikh sect comprised of mainly "untouchables," or Dalits.

Worshipper Mohnder Ram, 72, who has lived in Vienna for decades, said the temple that was attacked had been attended by followers of Shri Guru Ravidas, the 14th-century founder of the sect. Witnesses said the group of bearded and turbaned men raided the temple as the preachers led several hundred worshippers in prayer. Followers moved to defend their leaders.

"I heard four to five shots" in the temple, said Ram. "People started screaming, children were crying as they ran out. It was like war. There was lots of blood everywhere."

Six suspects are in custody, including four wounded and in serious condition, police spokesman Michael Takacs said, adding that more may be detained. The wounded were all of Indian origin and aged between 30 and 50, said Bernhard Segall of Vienna medical services. The most serious wounds were caused by gunshots to the abdomen and head.

The temple is housed in a residential building of the working-class neighborhood of Vienna-Rudolfsheim.

Ram said about 400 people were at the service when the fight broke out; police put the number at between 150 and 300.

The scene was "like a battlefield," Takacs said.

Nearby resident Bimla Lalka said she saw seven or eight men with long beards and dark blue and orange turbans fleeing the building.

Sikhs make up less than 2 percent of India's nearly 1.2 billion people.

Caste discrimination has been outlawed in India for more than a half century, and a quota system was established with the aim of giving Dalits a fair share of government jobs and places in schools. But their plight remains dire, living in poverty and kept down by ancient prejudice and caste-based politics.