Hong Kong’s top political leader has urged people to refrain from “radical actions” as small businesses geared up for a one-day shutdown and groups called for a boycott of work and classes on Wednesday to protest against a proposed extradition law.

The bill, which will allow mainland China to pursue fugitives as well as government critics in the former British colony, is due for a second round of debate on Wednesday in the 70-seat Legislative Council, which is dominated by pro-Beijing lawmakers.

Despite a huge protest march on Sunday that drew hundreds of thousands of people, the chief executive, Carrie Lam, said she remained determined to pass the controversial law.

Many at the protest on Sunday, from young parents pushing prams to retirees on walking sticks, expressed worries that the civil rights and freedoms guaranteed to Hong Kong under the “one country two systems” arrangement will be quickly eroded under the new law as China often uses non-political crimes to prosecute its critics.

“To oppose this bill, some have called for radical actions,” Lam said in a media briefing, referring to the clashes between protesters and police outside the legislature shortly after midnight on Monday, after a largely peaceful, nine-hour protest.

“No civilised society would want to see youngsters being pushed to the frontline to take radical actions,” she said. “I urge schools, parents, organisations, corporations and unions to think about this carefully – if they call for radical acts, what good would it do for Hong Kong society and our youth?”

Lam’s admonishment underscored the government’s anxiety about the unpopular bill, as hundreds of small businesses across Hong Kong pledged to close on Wednesday while unions as well as parents and teachers’ groups called for a boycott of work and classes so that people could join a protest outside the legislature.

The businesses are mostly small retailers such as cafes, book and grocery shops, travel agencies, florists, small hotels, but also include tutorial schools, publishers, interior design and IT shops, opticians, and dental and medical clinics.

The pro-democracy Hong Kong Professional Teachers’ Union called on members to join the protest on Wednesday and urged schools to allow teachers time off. Student unions of seven universities and colleges also said they would boycott classes and join the protest.

The Hong Kong aviation industry gathered 1,700 employees’ signatures in an online petition to demand its union initiate a strike to urge the retraction of the “evil” law amendment, while the union of the New World First Bus Company condemned the government for ignoring citizens’ voices and urged its drivers to drive slowly on Wednesday. The pro-democracy Hong Kong Confederation of Trade Unions, which has 190,000 members, also urged its members to stay off work for the day.

In anticipation of large protests, the secretariat of the Legislative Council told lawmakers in a memo on Tuesday that it has closed the designated protest area outside its building due to “high risk” that it will be stormed by protesters during upcoming meetings on the extradition bill.

Several churches will hold meetings to pray for the city’s leadership and peace for Hong Kong.

An online petition called for 50,000 people to surround the legislature at 10pm (1400 GMT) on Tuesday and stay until Wednesday morning, when the debate over the law is scheduled to resume.

The legislature’s chairman, Andrew Leung, told a media briefing on Tuesday that he would limit lawmakers’ debate on the extradition bill to 66 hours, meaning that the bill could be put to a vote on 20 June, reported Radio Television Hong Kong.