One of about 30 protesters who had been on hunger strike in an eastern Ukrainian city over pension cuts died Sunday night after police broke up their tent encampment, the protest leader said.

The group were survivors of Ukraine's Chernobyl nuclear accident and had been staging their protest in the mining city of Donetsk in eastern Ukraine since November 14 after reductions in the state pensions they receive for their part in fighting the 1986 disaster.

With temperatures hovering around zero, local emergencies ministry workers had provided one large tent with heating for the core protesters to sleep in until the issue had been resolved.

But after a court ruled the protest illegal late last week, police stormed into the main tent Sunday night and removed a power generator, a stove and cut off lighting, the protest leader Nikolai Goncharov told reporters.

In the ensuing disorder, 68-year-old Gennady Konoplyov was taken ill and died in an ambulance after the police operation, Goncharov said. It was not clear what he had died from and there was no immediate comment by police.

The police attack on the tent city was an act of terrorism, Goncharov said.

The incident is a personal embarrassment for President Viktor Yanukovich. Donetsk is his home town and normally a loyal bastion of support for him and his Regions Party.

All this has happened with the silent agreement of the guarantor of the Constitution, President Viktor Yanukovich of Ukraine. The death of our comrade will be on his conscience because the President arranged this mayhem, Goncharov said.

Reform of the ex-Soviet republic's bloated pensions system is one of the commitments that Yanukovich's government has had to make to the International Monetary Fund in return for a $15 billion stand-by program.

It is dragging its heels, however, on another promise to the IMF to raise the price of household gas which it fears will dent the popularity of the Regions Party before a parliamentary election next October.

The Chernobyl disaster-fighters, who were evacuated with their families from the northern region 25 years ago, have become a powerful action group against the government's austerity moves and regularly stage protests at the parliament building in the capital Kiev.

(Reporting by Lina Kushch; Writing By Richard Balmforth; editing by David Stamp)