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 military to begin Iran maritime blockade on Monday
The US Central Command said it will begin implementing a blockade of all maritime traffic entering and exiting Iranian ports on April 13 at 10 a.m. ET (1400 GMT), after President Donald Trump said the US Navy would start blockading the Strait of Hormuz.
Hungary's Orban concedes landmark election defeat
Hungary's veteran nationalist leader Viktor Orban conceded defeat on Sunday after a landslide election victory by the upstart opposition Tisza party, in a setback for his allies in Russia and US President Donald Trump's White House.
Trump vows to blockade Strait of Hormuz after Iran peace talks stumble
President Donald Trump said on Sunday the US Navy would immediately start blockading the Strait of Hormuz, raising the stakes after marathon talks with Iran failed to reach a deal to end the war, jeopardising a fragile two-week ceasefire.
Nigerian airstrike hits market, 200 feared dead
At least 200 people are feared dead after Nigerian military jets struck a village market while pursuing rebels in the northeast of the country on Saturday night, a councillor for the area and residents said on Sunday.
Russia, Ukraine trade accusations of ceasefire violations
Russia and Ukraine accused each other on Sunday of breaching the 32-hour ceasefire in their four-year war, reporting more than a thousand drone and shelling attacks just hours after the truce began on Saturday to mark Orthodox Easter.
