Eleven petrol bombs were thrown in Londonderry on Monday night
Eleven petrol bombs were thrown during disturbances after Monday's Orange Order parade in Londonderry.
Trouble flared near the Apprentice Boys Memorial Hall and Fountain areas from about 2200 BST. There have been no reports of injuries.
There were also minor disturbances during the return leg of the Twelfth parade in Londonderry.
Police had to deal with minor trouble in the Butcher's Gate area. One policeman sustained a slight injury.
Earlier, rival groups taunted each other as Orangemen and a small number of bands made their way through the Diamond area.
Both sides spat at each other and threw missiles. Police separated factions.
Officers remained in the area, and were attacked by nationalists throwing stones and bottles.
About 3,000 Orangemen and supporters were involved in the parade, the first to be held in Derry since 2005.
But a local business man said the parade had been bad for business.
Martin McCrossan, who runs walking tours of Derry, said many shoppers had stayed away.
There has been trouble in Londonderry, with petrol bombs being thrown
"They're not here to buy, they're not here to do business they're here to march and that's solely what they do," he said.
"So by the very fact of the nature of the organisation we have to be realistic - will it ever be acceptable to the Roman Catholic community?"
In Tyrone the main parade was in Dromore, with other parades in Coagh and Fivemiletown. Lisbellaw hosted the main Fermanagh demonstration.
In Derry the Orange Order had appealed for people to parade peacefully.
"There appears to be a lot less hostility this year, and we would appeal for absolutely no hostility towards ourselves or from anyone in our parade towards anyone else," said city Grand Treasurer William Wray.
"We are trying to encourage peacefulness across the city. It's something we're working hard towards and we've a lot more work to do.
"It's probably one of the largest free music festivals in Europe. I think the nationalist community could come along and enjoy that and I would encourage them to do that.
"In Londonderry we have tried to stay away from a politician coming and having a main speech. We try to keep it as neutral, and free from politics, as we possibly can."
Police in County Fermanagh have appealed for information following separate incidents at a church hall and Orange Hall.
Damage was caused to the door of a church hall in High Street, Newtownbutler. The incident was reported to police at 0900 BST on Monday.
Earlier on Monday, a tyre was set and against the front door of Wattlebridge Orange Hall and set alight at about 0300 BST.
An Orange Order spokesman said the burning tyre only caused smoke damage.