Last month 310 people were found trying to enter the State without meeting the normal entry requirements. All were refused entry, including nine who applied unsuccessfully for asylum.
The UN High Commissioner for Refugees said yesterday it was concerned about the implications of the clamp-down on asylum-seekers coming to Ireland.
According to the Government, however, the issues of illegal immigration and refugees or asylum-seekers are separate.
Under measures provided for under the Aliens Order introduced by the last government in June, there is a permanent Garda/Army checkpoint at Dromad on the Belfast-Dublin road.
In the last week the newly-appointed immigration officers have turned back seven foreign nationals who either had no passports or visas or else claimed they were "on holiday" but had no money with them.
The group included three Romanian nationals who were last month refused entry when they arrived at the North Wall in Dublin.
The people, stopped either at Dromad or at Dundalk railway station, were en route from Belfast to Dublin and were detected by one of the 11 gardai with special immigration powers.
Teams of gardai have also mounted spot checks on many of the Belfast trains arriving at Connolly station in Dublin.
In one check last week, three nationals from outside the EU were sent back to the North.
"Every garda can demand a passport of a foreign national but an immigration officer can refuse someone entry into the State," Garda Pat Tobin, who was working at the Dromad checkpoint yesterday, said.
All Ulsterbus, Bus Eireann and local bus services between Newry and Dundalk were being diverted to a weighbridge area adjacent to the checkpoint.
Spot checks are also taking place on trucks and lorries. "The seven people turned back either had no passports or visas," one of the Garda officers said. The UNHCR's liaison officer in Dublin, Mr Paolo Artini, said that while he was not critical of the Aliens Order per se he was concerned about its implications for asylum-seekers. The State had a duty to ensure that refugees had access to an asylum procedure somewhere.
He expressed concern about the lack of access to legal advice for people stopped under the new arrangements.
There was no appeal or translation facilities, and family links in Ireland were not taken into account, he said.
Mr Artini welcomed the Minister's decision to appoint an additional 72 staff to speed up the processing of asylum applications. A High Court judge has also been appointed to hear appeals against the refusal of refugee status.
There is a high percentage of foreign nationals on all trips between Dublin and Belfast. One Ulsterbus checked yesterday morning had six Germans, two Swiss, two French, one South African and one Chinese man on board.
A bus driver who had two passengers refused entry said: "One of the men got on in Belfast and I asked him where he was going. He said `Dublin' in an accent and I thought he was a Yank. When they stopped him here [Dromad], he hadn't a word of English." However, he said the checking was delaying journeys by up to 20 minutes and "it is a nuisance".
Since the end of June legislation had allowed for immigration officials to stop people coming into the Republic from Britain or Northern Ireland.
Of the seven people refused by the Dundalk-based officials, four were from eastern Europe, one came from Rwanda, one from Somalia and one from the former Soviet Union.
A spokesman for the Department of Justice said it was important that people realised the common travel area between the Republic and the UK had not ended.
"People who normally require a visa to enter Ireland are subject to the same checks as if they had arrived at Dublin Airport . . . There are 60 countries which require a visa to enter Ireland," he said.
The Garda Press Office would not say how many gardai have been appointed immigration officials or at which locations they have been posted.
A spokesman would say only that a number of gardai have been appointed and are employed at different locations along the entire Border from Louth to Donegal.