St Patrick's Day celebrations are in full swing across Northern Ireland.
Two children enjoy the festivities in Belfast
In Belfast, an open air concert is being held outside the City Hall, replacing the parade to the city centre.
The concert will feature the winners of the Irish Republic's Popstars television programme, Six.
The organisers said they hoped that the three-hour event would attract people from all parts of the community.
The Lord Mayor of Belfast, Sinn Fein's Alex Maskey, said that Monday's concert was an inclusive event.
"Respect and tolerance for what is a diverse community has to be the hallmark of everything we do here today," he said.
In recent years, celebrations of Ireland's patron saint have been hit by controversies over parades in Belfast.
Three years ago, the St Patrick's Day parade in Belfast was embroiled in a row over a lack of funding by Belfast City Council.
The council is not funding this year's concert, but it is due to hold another concert in the Ulster Hall in the evening.
Sinead Quinn talks to autograph hunters ahead of the Belfast concert
In Londonderry, a free outdoor concert has begun at the Guildhall Square.
The Furey Brothers will top the bill at the concert.
In Omagh, the Ulster American Folk Park will re-enact the era of emigration as part of its programme of events.
Up to 2,000 Orangemen will parade through Ballymena to commemorate Ireland's patron saint.
In St Patrick's burial place, Downpatrick, the Church of Ireland's celebrations will include a pilgrimage from Saul to Down Cathedral.
The Duke of York has flown into Northern Ireland to carry out a St Patrick's Day engagement with the Royal Irish Regiment.
Prince Andrew was presented with shamrock
Prince Andrew, who is colonel in chief of the regiment arrived at St Patick's Barracks in Ballymena on Monday morning.
He was presented with shamrock by the wife of the unit's commanding officer.
He later travelled to Hillsborough, where he met representatives of five Northern Ireland companies which won the Queen's award for export last year.
More than 500 Irish Guards on military service in Kuwait in preparation for possible war with Iraq have been presented with ceremonial shamrocks, according to a St Patrick's Day tradition which dates back to 1901.
The sprigs were starting to wilt in the desert heat, having travelled more than 3,000 miles after initially being picked in County Cork on Sunday.
Colour Sergeant Tommy Cassidy, from Belfast, said: "It's a big morale boost for the boys because no matter where they are, Arctic, desert or jungle, whoever the visiting dignitary is, they always make a point of presenting it.
"Normally it comes with a few cans of liquid refreshment but obviously not in this instance, but we will play catch-up later when we get back home.
Dublin held the biggest and most colourful parade in Ireland
"The boys like it. I think they will have a nibble of it later, and a little drink of water."
An estimated 500,000 people have turned out for the parade through Dublin city centre.
Ireland's biggest and most colourful parade is to march through Dame Street and O'Connell Street.
On Sunday, tens of thousands of people turned out in central London for the annual St Patrick's Day pageantry.
About 80,000 people are estimated to have attended the festival.
London's mayor Ken Livingstone is aiming to make the city's St Patrick's Day festivities as big as the celebrations in New York and Chicago.
Londoners enjoyed the celebrations on Sunday
The festival featured craft and food and drink stalls and a large stage with Irish music and dancing.
Mr Livingstone thanked the crowds for supporting the day.
"There's a lot of people living in London with not a drop of Irish blood in them", he said.
"But they still felt able to join in with the celebrations."