Gardai held back noisy demonstrators as the British Queen took part in a wreath-laying ceremony at the Garden of Remembrance in Dublin city centre.

There was minor trouble as republicans opposed to the visit and the peace process in Northern Ireland jostled with gardai.

At one stage two flares were lit and thrown into the air.

The ceremony, the first major engagement of the British monarch's visit, started on time but, with thousands of gardai lining the route along the city's main thoroughfares, the security operation was the biggest ever mounted in the history of the state.

Queen Elizabeth, who changed into a new outfit for the poignant and symbolic wreath-laying having arrived in Dublin in green, looked unperturbed as the ceremony took place at the Garden of Remembrance, which honours all those who fought for Irish freedom from British rule.

Snipers and armed gardai patrolled rooftops and a church spire overlooking the garden as spotter planes and the garda helicopter circled above.

Gardai maintained order at two separate protests on streets several hundred yards from the garden.

The largest gardai presence ever seen in the country was deployed the entire length of the route as the Queen and President Mary McAleese travelled for the commemoration.

The garden opened in Easter 1966 to mark the 50th anniversary of the 1916 Rising when seven signatories to Ireland's Proclamation of Independence, backed by the 1,000 strong Irish Citizen Army, launched a revolution against British rule beginning with the takeover of the GPO a few hundred yards away on O'Connell Street.