HONG KONG (Reuters) - Students in Hong Kong began a two-day strike at schools and universities on the first day of the new school year in an effort to exert more pressure on local authorities to heed demands to scrap a controversial extradition bill for China, release all detainees and resign the chief executive. For the country Carrie Lam.

The government in Hong Kong was counting on the start of the semester for students to attend school and universities, but hundreds of thousands are still on the streets chanting anti-government slogans and banners calling for freedom and democracy.

The city's metro lines have seen a heavy police presence after weekend clashes between protesters and police across the city, which led to the closure of several railways.

Police searches, especially for students, were also reported on social media, with plans to disrupt the Metro service.

Many pupils gathered outside their middle and high schools wearing school uniforms and gas masks as part of the planned strike action.

Anti-government protesters had called for a general strike and a rally today, but it was not clear how many would take part in heavy rains across the city.

The train operator in Hong Kong announced yesterday the suspension of trains to the island airport after a crowd of hundreds of protesters outside, which led to the disruption of traffic.

Roads were also congested after protesters urged people to take to the streets and flock to trains to the airport, one of the world's busiest.

The former British colony has been in its most serious political crisis for three months since it was returned to China in 1997, witnessing almost daily moves to denounce the erosion of freedoms and Beijing's rising interference in the affairs of this semi-autonomous city.

Beijing, which strongly supports the Hong Kong government, has stepped up intimidation with moves on the city's border and pressure on local businesses.

The official Xinhua news agency warned in an article on Sunday that "the end is approaching" for the democratic movement, without giving details.