Residents accounted for 74.8% of total arrivals at accommodation establishments in May, while foreigners made up for the reminder 25.2%.
The vast majority of foreign visitors (81.6%) came from Europe, the data showed.
Foreign tourist arrivals to Romanian borders declined 1.8% on the year in May, but Romanian tourist departures aboard rose 6.1%, INS said.
In the first five months of 2013, tourist arrivals at Romanian accommodation establishments rose 5.3% compared with the year-earlier period, while overnight accommodations edged down 0.2%.