By Luiza Ilie
BUCHAREST, March 8 (Reuters) - Thousands of miners from Romania's mountainous Jiu valley marched through the streets of Petrosani for the fourth successive day on Thursday in a pay protest, after the collapse of talks with the economy ministry.
Local media said some 5,000 miners from all seven Jiu valley mines took part, and a police spokesman said they had threatened to block the main road from Petrosani, their company's base, to the capital Bucharest, 340 kms (210 miles) to the southeast.
"As on previous days the protest was initially static, in the courtyard of the CNH, before the miners marched through Petrosani and headed for the national road," Nicolae Raducu, spokesman of the Hunedoara county riot police, said on Thursday.
"My colleagues have tried to persuade them to turn back but failed and ... the miners have been standing peacefully at the crossroads for the past two hours."
The miners' unions were were a potent political force in the early 1990s, when the state-owned industry employed almost half a million people, and many blamed violent miners' riots in Bucharest for the slowness of Romania's transition to democracy after the 1989 anti-communist revolution.
The miners' influence has shrunk considerably since the industry restructured in the late 1990s, leading to largescale layoffs, rampant unemployment, poverty and environmental degradation from which the Jiu valley region is still suffering.
The Jiu valley mines are managed by the state-owned National Hard Coal Company (CNH), a loss-making, highly subsidised firm that now employs just under 8,000 people. It is expected to lay off more staff under Romania's 5 billion euro aid package led by the International Monetary Fund.
The protests began on Monday when the miners demanded that the newly appointed government of Prime Minister Mihai Razvan Ungureanu enforce a pay protocol signed by the previous economy minister. The protocol included a rise in the bonus for miners working in dangerous conditions.
"We are deeply concerned over an imminent triggering of an extreme situation, which is why we are urging you to intervene and ... find solutions," the miners said in a letter to Ungureanu, according to a union leader quoted by the state news agency Agerpres.
Coal fires more than 40 percent of Romania's power plants, but most of it is lignite, which is softer than hard coal and is dug in open pits. Romania extracts about 3 million tonnes of hard coal and 33 million tonnes of lignite a year.
The government aims to merge the remaining viable hard coal mines with two generating plants that burn hard coal this year to create a new electricity holding company, and to close three outdated hard coal mines by 2017.
Romania's power sector needs reform to attract private investors as the economy ministry estimates it needs 30-40 billion euros of investment in new electricity generation. It will close one third of its outdated power capacity by 2020 and more than half by 2035. (Editing by Tim Pearce)