Activists

Mr Wong, who became the face of the 2014 Hong Kong street protests, had been hoping to speak to Thai students.

But the 19-year-old was detained on arrival at Suvarnabhumi airport and then flown back to Hong Kong.

He said there had been "no explanation for his detention", but activists attributed the decision to intervention from Beijing.

Mr Wong was at the heart of the mass demonstrations against Beijing that brought parts of Hong Kong to a standstill in late 2014.

Leonid Volkov, campaign chief for the opposition, and candidates Yegor Savin and Sergei Boyko began the strike on Tuesday after the election commission in Russia's third-largest city didn't accept the signatures they submitted to register to run in the upcoming local legislature vote.

The Local Coordination Committees says the attack on the town of Ihsim killed 17 people and wounded dozens.

The Britain-based Syrian Observatory for Human Rights said 18 were killed, including four members of the same family.

Syrian airstrikes carried out by warplanes and helicopters have killed thousands of people in recent years. The U.N. says that Syria's civil war has killed more than 220,000 people and wounded at least a million since the conflict began in March 2011.