Warnings of arrests as Serbian protesters descend on Belgrade

Thousands of protesters, mainly students, descended on Serbia's capital on Friday ahead of a planned weekend of massive anti-government rallies, many travelling hundreds of miles on foot or by bike.

President Aleksandar Vucic said he had asked police to show restraint, but to detain troublemakers. "The state ... will do everything to secure peace. Those who endanger peace will be arrested," he told a news conference.

Thousands of people cheered and waved Serbian flags as student columns started entering Belgrade city centre. Hundreds of bikers, parked near the parliament building, revved their engines in support. Cars honked as they drove by.

Supporters, including students from Belgrade, laid out a red carpet for the arriving protesters along the main Terazije boulevard.

"Belgraders, liberators have arrived," said Angelina, 19, a student from the northern city of Zrenjanin.

The rallies are expected to be the biggest in decades. Near daily student protests began in December following the deaths of 15 people when a roof at a railway station collapsed on November 1 in the northern city of Novi Sad, a disaster opponents blame on corruption under Vucic.

Authorities expect anywhere between 60,000 and 80,000 protesters to arrive to the capital, Vucic said. Organisers say they expect many more.

Students, teachers, farmers, and workers have joined the demonstrations in a major challenge to Vucic, a populist, in power for 12 years as prime minister or president.

Throngs of Vucic loyalists have arrived in Belgrade this week to camp near his office in the centre of the city. They brought tractors overnight to surround their camp.

Earlier, outgoing Prime Minister Milos Vucevic said police would intervene in case of violence.

Last December, students issued a set of demands that included the release of documents related to the railway station disaster and accountability for those responsible.

Prosecutors have charged 13 people over the disaster, and the government has announced an anti-corruption campaign. Vucevic and two ministers have also resigned.