The prime minister of Romania was indicted on Monday on charges of tax evasion and money laundering as part of a wide-ranging corruption investigation that has thrown the country into crisis.

Victor Ponta is also accused of conflict of interest and making false statements dating back to when he was a lawyer in 2007 and 2008, before he became prime minister in 2012.

At the time, Ponta was a lawmaker. He denies wrongdoing and says he has documentary proof of his innocence, according to the Guardian.

Prosecutors also said in a statement on Monday that they temporarily froze Ponta's personal assets. Ponta is the first sitting Romania prime minister to be indicted and have his assets seized.

It wasn't immediately clear if Ponta could be arrested. He has immunity for some of the charges, including the conflict of interest accusation. But he doesn't have immunity for the tax evasion and money laundering accusations.

Ponta, 42, who is recovering from a knee operation, was questioned at the offices of anti-corruption prosecutors on Monday morning. He walked up the steps on crutches into the building and when he emerged about 30 minutes later, he declined to respond to questions, citing his right to remain silent.

On June 5, prosecutors identified Ponta as a suspect in a corruption investigation, sparking political turmoil. President Klaus Iohannis urged Ponta to resign, but the prime minister refused. Ponta said he has not spoken with the president since June 5.

The situation has also caused tensions within Ponta's party, the biggest in Romania.

Ponta resigned as chairman of the ruling Social Democratic Party on Sunday, saying he wanted to prove his innocence.

Close ally Liviu Dragnea called that move a "mistake" on Monday, urging him not to quit as prime minister, a position he has held since May 2012.

Ponta survived a vote to lift his immunity and a no-confidence vote in June. He then went to Istanbul for his knee operation on June 15 and stayed for more than three weeks. He resumed his duties as prime minister on July 9.