Gerry Adams, the leader of Sinn Fein, said yesterday that the Queen's visit to Ireland this week could mark moves towards a new and better relationship between the country and Britain.

His remarks come as an unprecedented security operation begins in the republic to protect the Queen from terrorist attacks or street disorder.

The public will be kept back from the royal entourage as it passes along Dublin's quays, north of the river Liffey and the city's main thoroughfare, O'Connell St.

Adams said the three-day royal tour could provide "a unique opportunity" for mutual respect and equality on both sides of the Irish Sea.

His comments, in a column for the Irish Examiner, mark a change in his attitude to the historic visit.

He said he had nothing against the Queen but he was opposed to the idea of monarchies in principle. He hoped the visit would hasten the day when a new and better relationship could be formed, but that would depend on what the Queen said.

Adams maintained that the visit was troubling for many people and found suggestions that the state visit was an indication that Irish people had matured insulting and patronising. In March, the Sinn Fein president had described the visit as premature.

His comments came as security forces on both sides of the border began a clampdown on republican dissidents who have vowed to disrupt the visit.

In Northern Ireland, police arrested a man and a woman in County Armagh in connection with dissident republican activity.

Detectives from the Police Service of Northern Ireland's serious crime branch held a man of 25 in Lurgan and a woman of 26 in Armagh. Both are being questioned under the Terrorism Act.

Former IRA hunger striker and bomber Marian Price is still being quizzed about dissident republican actions by the PSNI. She was arrested at her west Belfast home on Saturday.

Price was seen at Easter standing beside a masked Real IRA man at a dissident republican commemoration in Derry. She has been a bitter critic of the peace strategy of Adams and Sinn Fein, regarding their stance as a sellout of traditional republican principles.

South of the border the Garda Siochana is continuing preparations for the arrival of the Queen and the Duke of Edinburgh.

More than 30 streets in central Dublin will have parking restrictions imposed throughout the week. Up to 5000 gardai will be deployed to protect the royal couple. The force also has water cannons in reserve, borrowed from the PSNI.

Barriers will remain in place throughout the royal visit and will keep the public away from the royal party, which will travel through the city in bulletproof cars.

Senior Garda sources have expressed concern over the continuing ability of dissident republicans to acquire sophisticated new arms from sources abroad.

They point to the seizure of a new type of mortar rocket launcher at Dublin airport at Christmas. The weapon is more accurate and has a greater range than launchers used in previous attacks on police stations in Northern Ireland.