The two -- a woman and a child -- died in Thailand's resort island of Phuket, a ministry official said, adding the government was trying to confirm a report that at least seven Japanese tourists were swept away in Sri Lanka.
The death toll in Asia from the powerful quake off Indonesia and massive tidal waves that it unleashed had so far reached 23,675 with officials in nine countries reporting deaths.
In Japan, an emergency survey of 17 major domestic travel agencies showed at least 22 of their 1,315 customers who went to the affected region were unaccounted for.
But the foreign ministry official said that number could rise.
Tokyo has urged travellers to postpone all but necessary trips to the tsunami-hit areas, saying visitors may face trouble due to damage to hotels, transportation and telecommunications.