The basilica, built over the grotto in Bethlehem where Christians believe Jesus was born, is administered jointly by Roman Catholic, Greek Orthodox and Armenian Apostolic authorities. Any perceived encroachment on one group's turf can set off vicious feuds.
On Thursday, dozens of priests and cleaners came to the fortress-like church to scrub and sweep the floors, walls and rafters ahead of the Armenian and Orthodox Christmas, celebrated in the first week of January. Thousands of tourists visited the church this week for Christmas celebrations.
But the cleanup turned ugly after some of the Orthodox faithful stepped inside the Armenian church's section, touching off a scuffle between about 50 Greek Orthodox and 30 Armenians.
Palestinian police, armed with batons and shields, quickly formed a human cordon to separate the two sides so the cleaning could continue, then ordered an Associated Press photographer out of the church.
Four people, some with blood running from their faces, were slightly wounded.