A trial has begun for a Japanese journalist charged with defaming South Korea's president by reporting rumors that she was absent for seven hours during a ferry disaster in April because she was with a man.

A spokesman from the Seoul Central District Court said Thursday that Tatsuya Kato of Japan's Sankei Shimbun was present in court as his lawyers and prosecutors introduced evidence.

The indictment has raised questions about South Korea's press freedom. Critics accuse South Korean President Park Geun-hye's conservative government of clamping down on journalists in an attempt to control her image.

Prosecutors indicted Kato in October over his Aug. 3 article about Park's whereabouts on the day the Sewol ferry sank and killed more than 300 passengers, mostly teenagers on a school trip.

The article repeated rumors in South Korean media and the financial industry about a relationship between Park and a former aide who was said to be married at the time. Kato, who has been placed under a ban from leaving the country, pleaded not guilty to the charges, according to court spokesman Kim Dae-hyun. The next court date was set for Dec. 15, Kim said.

The case has opened a debate on South Korea's freedom of speech and expression. Moon Jae-in, an opposition lawmaker who was Park's main rival in the 2012 presidential elections, told reporters on Tuesday that the prosecution's decision to indict Kato was an "embarrassment."

"Even if media outlets publish stories that are untrue or make arguments that are hard to agree with, it is important to allow the stories to be debated, criticized and naturally perish within the realm of the media," Moon said.