Up to 20 Irish people are understood to be among the 3,500 foreign tourists still unaccounted for three days after the Indian Ocean tsunami.
A spokeswoman for the Department of Foreign Affairs said that efforts to account for the missing people were being hampered by the region's "decimated" telecommunications network.
The Minister for Foreign Affairs, Mr Dermot Ahern said: "Relatives of people in the stricken region should understand that communications systems are down in many areas," he said this morning.
Over 68,000 people have now been killed by the earthquake-generated tsunamis that crashed ashore on St Stephen's Day in India, Indonesia, Sri Lanka, Thailand, Malaysia, Myanmar and the Maldives.
The were an estimated 500 Irish people on holiday or resident in the nine countries across the Bay of Bengal when the disaster struck.
The Department of Foreign Affairs said last night that of more than 2,000 calls made to its emergency helpline since the disaster, "between 10 and 20" cases had not yet been resolved.
"From the calls we are getting - we got 1,000 calls to lines over the last 24 hours - we estimate there is about 500 people in the affected areas altogether," the Minister said.
"There are approximately five to ten people who are receiving medical care but it's a bit difficult to estimate what the situation is because most of these countries don't require a visa," he added.
But a Department spokeswoman stressed that most of the 700 individuals about whom concerns had been raised were now accounted for successfully. About half the calls to the Department concerned people in Thailand.
The Department is continuing to operate its helpline at 01-4082308, and has appealed to those whose relatives have contacted them to tell the Department.
At least 473 foreigners were killed in Thailand alone, Thailand's Department of Disaster Prevention and Mitigation said. Other estimates have put the total number of foreigners killed around Asia at 174.
The missing include at least 1,500 Swedes, 800 Norwegians, 214 Danes and 200 Finns escaping the frigid Nordic winter.
Apart from the Scandinavians, authorities had lost track of 200 Czechs, 188 Israelis, 100 Germans and 100 Italians. More than 400 Singaporeans could not be contacted.
More than 3,000 people may have died at Khao Lak, a Thai beach resort north of Phuket island and especially popular with Scandinavians and Germans. Over 1,200 bodies have already been recovered.
More than 300 bodies were found on Thailand's Phi Phi island, made famous by Leonardo DiCaprio's film The Beach, which was devastated by a series of powerful waves.
The 14-year old granddaughter of British actor and film director Richard Attenborough was among the dead, and his daughter and her mother-in-law were missing.
Additional reporting: Reuters
The Minister for Foreign Affairs, Mr Dermot Ahern warned that it could be "days if not weeks before a clearer picture emerges" of how many Irish people have been affected.