Hundreds of young Japanese fans, many wearing witch costumes and holding magic wands, screamed when Daniel Radcliffe appeared as white smoke spewed on the stage.
"Japanese fans are the best!" Radcliffe, dressed in a white suit, said in simple Japanese.
"Order of the Phoenix" was directed by David Yates, a Briton best known for the multilayered TV thrillers "State of Play" and "Sex Traffic."
The film opens as Hogwarts School of Witchcraft and Wizardry is undergoing a gradual takeover by the bureaucratic Ministry of Magic and its emissary, Defense Against the Dark Arts teacher Dolores Umbridge (Imelda Staunton).
Photos: Promoting "Potter"
A sense of impending doom is heightened by a series of nightmares that link Harry (Radcliffe) ever more closely to the devilish Voldemort, bringing Rowling's saga into even darker territory.
There's also a new love angle: Harry's first kiss with fellow student Cho Chang (Katie Leung).
The Harry Potter books have been translated into 65 languages and sold more than 325 million copies since the first volume, "Harry Potter and the Philosopher's Stone," was published in 1997. (The book was published in the United States with the title "Harry Potter and the Sorcerer's Stone.")
After this movie, the next Harry-related frenzy will be the publication of the seventh and final book, "Harry Potter and the Deathly Hallows," on July 21.
The first Harry Potter movie was released in 2001. Radcliffe and co-stars Emma Watson and Rupert Grint, who play Harry's friends Hermione Granger and Ron Weasley, have been at the center of the Potter storm for almost half their lives.
"It's just absolutely brilliant. He's an icon," said 17-year-old Radcliffe, explaining why he's been playing Harry for such a long time. "He is somebody whose character has gotten his generation of kids into reading. So it's an honor to play him."
All three stars have signed up for the final two Potter films.
"Harry Potter and the Order of the Phoenix," a Warner Bros. Pictures release, opens in the United States on July 11 and in Britain the next day.