Several dozen police patrolled outside the Deutsche Oper, a modern building in western Berlin, before and during Monday's performance. Authorities said no incidents were reported at the performance.

Plainclothes officers also mingled with the audience, who had to pass through airport-style metal detectors in the foyer.

"We have never provided so much security for a performance of an opera," said police spokesman Bernhard Schodrowski.

The only demonstrations outside the building were in favor of freedom of expression.

Head scene met with mixed reaction

The staging of "Idomeneo" by director Hans Neuenfels culminates in a scene in which King Idomeneo places the blood-spattered heads of the Greek god Poseidon, Jesus, Buddha and Mohammed on four chairs.

The appearance of the heads in Monday's performance was greeted by a ripple of applause, with several boos when the head of Mohammed was brandished, according to audience reports.

The opera house had pulled the performance from its scheduled November slots in September because of fears it could spark demonstrations by Muslims angered by the depiction of Mohammed.

The manager of the opera house, Kirsten Harms, said she had acted on warnings from security officials. The opera was rescheduled after police said there was no "concrete risk" to security.

Many observers, however, thought the decision to cancel smacked of giving in to extremists and censoring artistic expression after the uproar over cartoons of Mohammed, which were first printed in a Danish newspaper.

Attendance a political decision

The German government had hoped to present a united, multi-cultural front at the performance, but two leading Muslim representatives turned down invitations to attend.

Ali Kizilkaya, who leads the Islamic Council of Germany, said he would not go because he feared the attendance of Muslim leaders was being seen as a measure of how "integrated" they were in society.

"It all seems to be done under the proviso that only those who go to the opera are integrated and those who don't go are not," he said.

Aiman Mazyek, head of Germany's Central Council of Muslims, said he did not want to become a "political pawn."

But the leader of the country's Turkish community, Kenan Kolat, was in the audience and criticized those who had stayed away.

"I greatly regret that some leaders have not come," he said. "They have missed an opportunity to send a message to the whole of society."

Kolat said art "must be free even if sometimes it is hard to accept."

German Interior Minister Wolfgang Schäuble said he "respected" the Muslim leaders who had refused to attend, but his ministry said earlier that nine of the 15 Muslim representatives invited would be present.

A second performance of the opera is scheduled for Dec. 29.