Roman Catholic and Orthodox clerics have exchanged blows inside Jerusalem's Church of the Holy Sepulchre, one of Christianity's holiest sites.
Two Muslim families guard the key to the only entrance
The punch-up began after Greek and Russian Orthodox believers took offence at a door left open by members of the Franciscan order during a service.
At least five people were injured in the fracas - including Israeli police officers called in to quell it.
The church is shared jealously by six rival Christian sects.
The Church of the Holy Sepulchre in Jerusalem's Old City is said to be the site of both the crucifixion and resurrection of Jesus Christ.
The latest trouble began after a procession through the church on Holy Cross Day - marking the discovery of the cross which some believe was used for the crucifixion.
"There was lots of hitting going on. Police were hit, monks were hit ... there were people with bloodied faces," said Aviad Sar Shalom, an Israeli tour guide who witnessed the fight, according to Reuters news agency.
Police said they made several arrests.
The six Christian sects sharing the church have come to blows before.
In 2002, monks from the Ethiopian Orthodox Church and the Coptic Church of Egypt - two groups which for years have been vying for control of the church's roof - fought over the position of a chair on the roof.
Rivalry between the six different churches dates back to the aftermath of the crusades and to the great schism between Eastern and Western Christianity in the 11th Century.
To prevent squabbling, two Muslim families have had guardianship of the key to the only entrance to the church since 1178 when they were entrusted with it by the Muslim ruler Salah el-Din (Saladin).