In monthly comparison terms, consumer prices edged down by 0.2% last month after a slip of 0.3% in April, NSI said in a monthly report.
Compared to the previous month, prices in May declined the most in communications, by 1.5%, followed by recreation and culture with a 1% fall. In contrast, the highest monthly price increase was registered in alcoholic beverages and tobacco, at 1%.
Bulgaria's inflation rate since the beginning of the year stood at 0.4%, while the average annual inflation for the past 12 months was 5.1%, NSI data showed.
Annual inflation under the Harmonised Index of Consumer Prices (HICP), which allows comparison on the same terms among all EU member states, sped up to 2.7% in May from 2.5% in April. In monthly terms, EU-harmonised consumer prices remained unchanged last month after dipping by 0.1% in April.