Romania's prime minister, who is under the spotlight in a corruption investigation, has taken medical leave after a knee operation in Turkey, leaving his deputy in charge.

Critics have called Victor Ponta a coward for using a routine medical problem to avoid the probe. President Klaus Iohannis asked Ponta, who survived a vote to lift his immunity and a no-confidence vote, to resign.

Ponta did not appear Monday before anti-corruption prosecutors who suspect him of conflict of interest, tax evasion and forgery.

Ponta suggested he would not return to Romania for three weeks and justified his absence by saying he hadn't taken a day off since becoming prime minister in April 2012.

Prosecutors have intensified an anti-corruption drive in recent months, earning praise from the U.S. and the European Union.