Beijing's public security chief has publicly stated for the first time that the anti-Japanese protests on April 9 there were illegal, and underscored that authorities will crack down on any other unlawful acts, a local newspaper reported Friday.

"We fully understand the public and students' patriotic feelings," Ma Zhenchuan, director general of the Beijing Municipal Public Security Bureau, was quoted as saying by the Beijing Evening News.

"But the April 9 demonstration itself was carried out without permission, and was illegal," he said, referring to the protests that included the pelting of Japanese diplomatic institutions with stones, food, ink and water bottles.

Ma warned about taking part in further unapproved demonstrations, as rumors swirled that a fresh round of protests may take place during the weeklong holiday from Sunday.