TOKYO - In an unusual public clash between Japan's imperial family and the media, the second son of Emperor Akihito has denounced as "baseless" a magazine report alleging he had a close relationship with a Thai woman.

Prince Akishino, who turned 31 yesterday, raised eyebrows in April by skipping a royal banquet honoring President Clinton to travel to Thailand.

The prince said a previous commitment to attend a Thai festival forced him to miss the banquet. But the gossipy weekly magazine Shukan Shincho claimed that the prince, who married in 1990, was on "intimate" terms with a Thai woman.

At a news conference Friday, Akishino said reports about his relationships with other women are "baseless" and "completely contrary to the facts." He did not mention Shukan Shincho by name but left little doubt he was referring to the magazine.

"Smoke has risen where there is no fire," the prince said in comments reported by Japanese newspapers yesterday. "Whoever wrote the story must have an extremely vivid imagination."

Akishino's wife, the former Kiko Kawashima, sat at his side during the news conference but did not comment. The couple has two daughters.

The editor of Shukan Shincho, Hiroshi Matsuda, said, "I have absolutely no intention of issuing a correction. . . . I still believe the story is true."

The Japanese media generally treat the royal household with extreme deference. The closest precedent to the latest clash came three years ago when Empress Michiko, Akishino's mother, issued a statement saying she was "deeply saddened" by untrue reports about her.

Shortly afterward the empress had a breakdown and was unable to speak for several months, a condition palace officials blamed on the critical articles in weekly magazines.

Akishino went even further than his mother, however, by making his criticisms at a news conference and denying specific allegations.

Matsuda defended his decision to print the article, saying the prince's absence from the Clinton banquet could have offended Japan's most important ally and therefore needed to be explained.

Japan's mainstream press has been much more circumspect. Even the prince's comments earned only brief mention in most newspapers.

Akishino is second in line to the throne after Crown Prince Naruhito, who is married to Harvard-educated Crown Princess Masako, a former diplomat.