"We urge all parties to exercise maximum restraint and avoid confrontation," Dujarric said.
The spokesman added that UN officials had been in contact with interlocutors on both sides, emphasizing "the need to allow people to demonstrate peacefully."
The Hamas-run Gaza health ministry, as quoted in a report by the Times of Israel, said on Friday evening that six men were killed and 922 injured people were taken to hospitals and field clinics.
Photographs published by the Agence France-Presse news agency showed protesters dodging tear gas canisters amid walls of thick black smoke from burning tires — dense enough in some places to completely obscure the border fence.
Israeli officials claimed the smoke provided a diversion in which groups of protesters stormed the fence in an attempt to open a fissure that would allow the crowd to push into Israel, according to the report.