The clash involved members of several rival Sikh temples in Vienna who had been feuding for several years, local authorities and witnesses said.

Authorities in Punjab have imposed a curfew on parts of the state, and the army was placed on standby after the protests broke out.

Appeal for calm

"The situation remains tense but under control," R K Jaiswal, a senior superintendent, said.

The attack in Vienna is the first act of violence involving Sikhs in the city [EPA]
Manmohan Singh, India's prime minister, said he was "deeply distressed" by the violence and issued an appeal for calm.

The violence in Austria came as preachers led several hundred worshippers in prayer, witnesses said.

Witnesses said a group of men had attacked two spiritual leaders, or gurus, who had travelled from India for the ceremony, and their followers had moved to defend them.

The two preachers were low-caste Sikhs, belonging to the Dera Sachh Khand group.

Leaders at the temple have campaigned against the caste system, angering other Sikhs in Austria who believe the correct traditions have been broken.

'Severely wounded'

Michael Froschl, an Austrian radio reporter, told Al Jazeera: "This is the first act of violence involving Sikhs in Vienna.

"This religious fighting has come as a shock to the city, as the area is multi-cultural and lives normally go on here without violence.

"The full details of the attack are unclear as most of the injured were severely wounded and have been unable to talk to police."

A police spokeswoman said six suspects, of whom four were wounded and in serious condition, had been arrested.

The possibility that not only the attackers but also some of the worshippers were armed was being investigated.

The Sikh community has about 2,800 followers in Austria.

About 25 million people observe the Sikh faith worldwide, most of them in northern India.