The Mass Transit Railway (MTR) said in a statement that the train service has been disrupted on the Airport Express due to someone trespassing and foreign objects on the track near the Airport Station.
"For safety reasons, train service has been adjusted because a number of facilities were damaged at various stations," MTR said.
A large group of protesters has been hurling numerous iron poles, bricks and rocks on the railway near the Airport Station since 4:00 p.m., with some even breaking on to the track, according to the police.
The protesters are participating in an unauthorized assembly, police said, adding that since an injunction order is in force at the airport, the protesters may be liable to "contempt of court."
Updated at 3:35 p.m. BJT
Since 1:00 p.m. local time, a group of protesters started gathering around bus stops at the Terminal of Hong Kong International Airport, the police said.
At around 2:00 p.m., protesters charged at barriers, pointed laser beams at the Airport Authority workers, and blocked roads with trolleys and mills barriers.
The police issued a warning, urging all protesters to stop their illegal acts and leave immediately.
Updated at 3:05 p.m. BJT
Sections of the Airport Express in Hong Kong were suspended on Sunday, according to the Mass Transit Railway (MTR) operator.
A notice at subway stations said the suspension was requested by the Hong Kong SAR government and the Airport Authority.
Hong Kong Station, from where the Airport Express starts, has been closed, according to CGTN reporter He Weiwei at the scene.