China has threatened to punish a local human rights group linked to five women's activists who were released on Tuesday. The foreign affairs ministry said Yirenping had "violated the law" but gave no further details. The group has been locked out of its Beijing office after the police conducted a raid last month. China earlier this week freed the women after more than a month in detention, a move welcomed by rights groups. The detention of the women, who planned protests against sexual harassment, had sparked an international outcry. In a daily press briefing on Tuesday, the foreign affairs ministry spokesman Hong Lei said the activists were from Yirenping and that the organisation "will be punished for violating the law". The details of the allegations and the punishment threatened were not given. Yirenping's co-founder Lu Jun told the BBC's Beijing bureau that he was looking for lawyers to address the allegations, adding: "We believe we have done everything legally." Mr Lu, who is currently based in New York, said that police officers had broken down the door of their Beijing office in the early hours of 24 March to conduct their raid. "My colleagues can't get into the office any more because the lock has been changed. I have pushed for an answer about who did this. The local police did not admit to it but said higher authority did it," he said. Also known as the Beijing Yirenping Centre, the group has offices in Beijing as well as Hangzhou, Shenzhen and Guangzhou. It was founded in 2006 to "promote public health, eliminate discrimination, and defend the right of disadvantaged groups through legal means", according to its website. It focuses on helping those with HIV and hepatitis B, women and disabled people bring anti-discrimination lawsuits against the government, companies and schools. It had lobbied for the release of the women, who were arrested shortly before International Women's Day on 8 March. Mr Lu had earlier said their detention was "a glaring injustice". The women had planned activities including a march in a Beijing park where participants would wear stickers advocating safe sex, and gatherings in Beijing and Guangzhou calling for awareness of sexual harassment on buses. The US, UK and European Union had all called for them to be freed. The five have not been charged but their bail conditions mean charges could be brought at a later date. Their lawyer also said they would need to update the authorities on their whereabouts. Rights groups said that their release showed that international pressure had worked, and called on China to drop all restrictions and threat of charges.