Two buses were also attacked, the Belfast Telegraph reported, with one driver hurt by flying glass after one of his windows was broken with a brick. Bus service was temporarily halted in east Belfast after the hijackings.
The protesters threw Molotov cocktails at St. Matthew Catholic Church and houses in the Short Strand, a Catholic area in east Belfast entirely surrounded by unionist neighborhoods. Witnesses said participants in a meeting at the church fled, although no injuries were reported.
Earlier Monday, business leaders, officials and Chief Constable Matt Baggott urged an end to the violent protests that began in early December when the City Council voted to fly the British flag at City Hall only 17 days a year. They warned tourists are being frightened away and said a teachers' conference scheduled for next November in Belfast has been canceled.
"You are not showing respect for the Union flag if you need to wear a mask when carrying it," First Minister Peter Robinson, leader of the Democratic Unionist Party, said. "For many the issue of the flying of the Union flag at Belfast City Council is now a cynical cover for the real political agenda, which is to destroy the political process."
Jim Wilson, a longtime community worker in east Belfast, told the BBC many loyalists in the area are "living in fear" because of the actions of the protesters. He said they fear the violence will bring a response from the Short Strand.
"I live here, my grandchildren live here," he said.