The European Central Bank (ECB) kept key interest rates unchanged as expected on Thursday in Frankfurt, but ECB President Jean-Claude Trichet signaled an increase in June

The ECB's 19-member governing council decided to hold interest rates unchanged after raising its main refinancing rate to 3.75 percent from 3.50 percent on March 8.

However, Trichet signaled another rate rise due to inflation risks. "I would not say anything today that would be aimed at changing expectations for June," Trichet told a press conference.

His remarks were in line with analysts' expectations that another rate hike was likely in June.

Trichet reiterated that the 13-nation euro region is in a period of robust growth and the central bank's monetary policy remains "on the accommodative side."

Trichet warned that higher oil prices and a hike in wages could pose risks to price stability.

Euro region inflation stood at 1.9 percent in March, within the ECB's 2-percent target.