* Explosion heard in capital
* Yugoslav-era power plant Kosovo's second largest
* Long slated for shutdown (Updates casualties, energy supplies)
By Fatos Bytyci
OBILIC, Kosovo, June 6 (Reuters) - A hydrogen tank exploded at Kosovo's second biggest power plant on Friday, killing at least one person and injuring 13, officials said.
The 40-year-old Kosovo A plant, considered one of the worst polluters in Europe, was shut down following the blast that was heard in the capital, Pristina, some 10 km (6 miles) away.
The explosion threatened electricity supplies in a country already plagued by blackouts. Power imports were increased to cover demand.
Authorities said the death toll might rise, while local media reported three dead.
"We have removed one body," Arsim Gerxhaliu, the head of Kosovo's forensics department, told Reuters by phone from the scene.
"But we had to leave the badly damaged building as there's a danger another tank may explode," he said. "We don't know how many other bodies are inside."
The Yugoslav-era plant and the larger Kosovo B account for 90 percent of electricity generation in the Balkan country, which still suffers chronic power shortages 15 years after breaking free of Serbia in a 1998-99 war during the collapse of federal Yugoslavia.
Costly plans to build a new plant that would allow Kosovo A to be closed for good have been delayed for years, with some critics blaming the government for toying with the rules of the tender.
Kosovo's main political parties canceled final campaign rallies planned for Friday before a parliamentary election on Sunday.
Health Minister Ferid Agani told reporters that 13 people had been treated for injuries that he said were not life-threatening. He said he had unconfirmed information about "some fatalities".
Economy Minister Fadil Ismajli, whose ministry covers the energy sector, told Reuters that the 345 megawatt (MW) Kosovo A had been shut down. The blast occurred in the electrolysis unit, not the generators.
Kosovo's energy distribution and supply company, KEDS, said it had imported 250 megawatt-hours (MWh) of electricity to cover demand. Spokesman Guri Shkodra told Reuters it was unclear when the plant would be back online.
Albania's energy ministry said it has started sending 50 MW of electricity out of 200 MW per day demanded by Kosovo to help it cope with shortages.
It said Albania's power utility KESH and power distributor OST and their counterparts in Kosovo were trying secure interconnection capacities to meet the need for the requested power.
Kosovo is connected to Albania via a 220 kV line. Work is under way to build a more powerful 400 kV line.
Last year, international donors pledged 154 million euros ($209.67 million) to help close down Kosovo A, improve energy efficiency and diversify energy sources in the landlocked Balkan country, one of Europe's poorest. ($1 = 0.7345 Euros)
The European Commission says the cost to decommission the plant, which produces a quarter of electricity consumed in Kosovo, is seen at 60 million euros, and that the commission is ready to ask member states to fund the project. ($1 = 0.7345 Euros) (Additional reporting by Maja Zuvela in Sarajevo and Benet Koleka in Tirana, Writing by Matt Robinson, Editing by Angus MacSwan)
The official said authorities believe the blast at Kosovo A power plant was caused during a botched replacement of hydrogen canisters used for cooling generators. The powerful blast was heard in the nearby capital, Pristina. A black plume of smoke could be seen rising from the coal-fired plant, as ambulances ferried the injured to hospitals.
Kosovo's civil emergency force said the body of one worker was retrieved from the site of the explosion and that other victims were being sought.
Police initially sealed off the area, fearing more explosions could follow emergency services dealt with the threat of further explosions and that the area was safe. Kosovo's prime minister, Hashim Thaci, who visited the site of the blast, said all the workers were evacuated from the complex.
The blast comes just days before a general election that has heightened tensions between rival parties amid allegations of corruption and embezzlement of public funds.
In the wake of the tragedy, Kosovo's main political parties suspended campaigning for Sunday's poll.
Nebi Qena in Donetsk, Ukraine, contributed to this report