The police have come under petrol bomb attack in Londonderry.
10,000 Apprentice Boys and 120 bands will march in Londonderry
No-one was injured in the attack, which happened as an Apprentice Boys bannerette was being dedicated in Society Street.
Meanwhile, the Apprentice Boys parade to commemorate the anniversary of the 1689 Siege of Derry is being held.
It is Northern Ireland's biggest annual loyal order parade. About 10,000 Apprentice Boys accompanied by 120 bands are on the march in Londonderry.
In the first parade, local Apprentice Boys and three bands walked the city's historic walls before a wreath laying ceremony in the Diamond.
The main demonstration is now under way.
It will last for several hours and was preceded by a religious service and a pageant re-enacting the siege.
The parade has been relatively trouble free in recent years.
The police have said they are visible on the ground and will have some areas in the city centre screened off to keep rival groups apart.
The loyal order commemorates the 13 apprentice boys who shut Derry's gates at the start of the siege by the troops of the Catholic King James II in December 1688.
The siege was finally lifted in the summer of 1689.