The wife of a Hong Kong environmentalist on Monday condemned Japanese authorities for having detained her husband and three other Greenpeace International campaigners in Tokyo since last Tuesday without bringing any formal charges against them.

"It's inhumane," a sobbing Phoebe Lam told reporters after protesting at the Japanese Consulate General in Hong Kong to demand the immediate release of her husband, Clement Lam, and the three other activists from Belgium, the Netherlands and Britain.

She said Japanese authorities have not allowed her to contact her husband.

Clement Lam, a Hong Kong-born Canadian, and the other three activists were detained by police last Tuesday after scaling a tower near an incinerator plant in Tokyo to protest the nation's waste-incineration policies and its dioxin problem.

The four were reported to have been transferred to the "Daiyo Kangoku" substitute prison system on Friday, where they can be questioned alone for hours by police without the questioning being monitored.

On Thursday, the police raided the Greenpeace flagship Rainbow Warrior and the Greenpeace Japan office in Tokyo, and seized documents.

The 555-ton Dutch-registered Rainbow Warrior was berthed in Tokyo as part of an Asian tour campaigning for a toxic-free Asia.

"My husband and the other three activists are not criminals," Lam said. "They just brought out the message that Japan has the highest levels of dioxin emissions in the world."

Their action was for the good of the Japanese public and their country, she noted. She criticized the Japanese government for having "overreacted" to the incident. About 12 Greenpeace members in Hong Kong joined Lam's protest.