Masked men attacked passengers after storming a train station in Hong Kong's Yuen Long district on Sunday.
Police say dozens of people are injured with one person in critical condition.
It comes after the latest pro-democracy rally in the centre of Hong Kong.
Demonstrations were also protesting against a controversial bill that allows extraditions to mainland China.
It's still unclear who the mob was or why the attacked the passengers.
US considering 'winding down' military efforts in Iran war, says Trump
President Donald Trump said on Friday the US was getting very close to meeting its objectives as it considers winding down its military efforts in the Iran war and called on countries that use the Strait of Hormuz to guard and police it "as necessary".
US sending marines and amphibious assault ship to Middle East
The US military is deploying thousands of Marines to the Middle East, officials told Reuters on Friday, as President Donald Trump accused NATO allies of cowardice over their reluctance to send forces to help open the Strait of Hormuz.
Fire breaks out at Kuwaiti refinery after drone attacks
The Kuwait Petroleum Corporation (KPC) has announced that the Mina Al-Ahmadi Refinery, operated by Kuwait National Petroleum Company (KNPC), came under drone attacks early on Friday, with a fire breaking out at several units as a result.
US strike against alleged drug smugglers in eastern Pacific kills two
US forces launched a strike against a boat allegedly involved in drug smuggling in the eastern Pacific, the US military said on Friday, killing two people.
UK says vaccine protects against strain in deadly meningitis outbreak
Britain's health authorities said on Friday that early laboratory analysis had showed the vaccine being offered to students should protect against the strain of meningitis behind an outbreak in southeast England that has killed two people.
