Hong Kong's Chief Executive has said he will review the city's criminal notification system with mainland China after thousands protested last Saturday over the case of the missing booksellers.
Mr Leung Chun Ying, who faces mounting pressure to address Hong Kongers' concerns of the possibility that one of the booksellers had been taken from Hong Kong by Chinese agents, also pledged to take up the case with Beijing.
To reassure Hong Kongers that only the city's authorities can carry out enforcement in Hong Kong, Mr Leung said he would " write to the central government immediately".
He also vowed to review the city's detention notification arrangement with the mainland, which he said "has room for improvement", after Chinese authorities apparently took months to provide information about the missing booksellers.
And "if it's necessary", he would send government officials to Beijing to follow up on the matter, said Mr Leung, who chaired an inter-department meeting on the Causeway Bay Books saga yesterday immediately after returning from a nine-day holiday.
The latest revelations by Mr Lam Wing Kee, one of the five booksellers who were reported missing last year only to resurface on the mainland this year, led to a street protest by some 6,000 people last Saturday.
Yesterday, the pan-democrats initiated a street petition calling for the release of all stakeholders of Causeway Bay Books store detained on the mainland. Apart from Mr Lam, 61, three others had been allowed to visit Hong Kong - they reportedly returned to the mainland - and one, Mr Gui Minhai, is known to be still in Chinese custody.
The five booksellers ran a publishing firm and Causeway Bay Books store, which specialises in salacious gossip about Chinese leaders.
Mr Lam's startling account at a press conference last Thursday of his eight-month detention on the mainland and how his business associate, Mr Lee Bo, 65, was apparently kidnapped in Hong Kong, led to a public outcry that the Basic Law, the city's Constitution, which allows only its authorities to carry out enforcement, was violated.
Yesterday, Chinese tabloid Global Times reported that Mr Lam had ulterior motive in his recent expose, giving the opposition parties in Hong Kong an opportunity to stage protests and deepen the rift between the city and the mainland.
Lawmaker Sin Chung Kai told The Straits Times yesterday that his Democratic Party will raise the issue at the weekly Legislative Council meeting tomorrow.
Mr Sin is doubtful of Mr Leung's measures, which he said should have been implemented last December, when the missing booksellers' case erupted. Nevertheless, he said, the Chief Executive "should explain to the Legislative Council his detailed action plan".
Dr Lam Wai Man, an honorary assistant professor at the department of politics and public administration at the University of Hong Kong, said that given the political nature of the incident, it would be difficult to assess the effectiveness of the measures.
"Because it is very much a political incident and it itself has been very much politicised, it is very hard to tell whether such incidents can be prevented in the future," Dr Lam told The Straits Times.
"The whole mechanism behind the incident is not transparent... Of course, there are people who know, but they won't tell."
While it was better for the Chief Executive "to do something rather than nothing", Dr Lam questioned the extent to which the measures would be carried out and the effectiveness of sending officials to Beijing to look into the case.
"There is a lot of mystery surrounding this case. No other official has the power to discuss it with Beijing. Only the Chief Executive can."