UPDATE 1-Romanian PM warns protesters on fifth day
* Romania's most violent protests in more than a decade
* 59 injured at weekend, hundreds gather again on Monday (Adds detail on Monday protests, PM comment)
By Radu Marinas and Luiza Ilie
BUCHAREST, Jan 16 (Reuters) - Romania's prime minister warned anti-austerity protesters gathering for a fifth day on Monday that violence would not be tolerated after 59 people were injured in clashes between demonstrators and riot police at the weekend.
The country's worst unrest for more than a decade has seen riot police using tear gas against protesters throwing bricks, smashing windows and setting fire to newspaper stands and rubbish bins in central Bucharest since it began on Thursday.
Thousands of demonstrators gathered peacefully in central Bucharest and other cities on Monday afternoon, demanding Prime Minister Emil Boc and his close political ally President Traian Basescu resign.
The numbers were expected to rise in the evening and analysts predicted more protests but did not see them affecting the austerity measures passed by the ruling coalition's small but stable parliamentary majority.
The country had hitherto avoided the kind of violence that has shaken Greece and other indebted European states despite a 25 percent cut in public sector pay and five percentage point increase in VAT imposed in 2010 to maintain an IMF-led bailout.
Boc, whose popularity is declining ahead of parliamentary elections late this year, said any violence would just end up harming the country.
"We have achieved stability but we cannot harvest the fruits immediately," he said in his first speech since the protests began. "My message is clear: violence will not be tolerated, peaceful protests are legitimate," Boc said.
"Street violence can do us much harm and can hamper prospects for economic growth."
People rallied initially in support of a deputy health minister who quit in protest at a controversial draft healthcare legislation. But the demonstrations grew despite the government's cancellation of the bill and evolved into a general expression of discontent with austerity policies and poverty.
"Five years of European Union membership did not bring anything good, on the contrary, poverty, frozen pensions," Ioan Mendea, a 73-year old former jurist, who ekes out a living from a 900 lei ($260) monthly state pension, told Reuters.
"This government, prime minister, president must go."
Markets were largely unfazed by the violence and the finance ministry managed to sell far more debt than planned at a tender.
Daniel Hewitt of Barclays Capital in London said the protests had so far had limited impact. "This is certainly a change, but it does not seem to be able to lead to any ... significant changes as it stands now."
Police said they had fined or started criminal investigations against 283 demonstrators involved in Sunday's violence. Along with the tear gas, it was not clear what other measures they could employ to prevent any future violence.
"Compared to the rest of Europe, the protests we have seen here were very small, they are not a proper instrument yet," said Cristian Patrasconiu, a political commentator. "But I do expect them to continue...This is a wave that has yet to break." ($1 = 3.4244 Romanian lei) (Editing by Philippa Fletcher)