OPPOSITION supporters in Belarus were warned yesterday that they could face the death penalty if they took part in a protest after the presidential election on Sunday.

Stepan Sukhorenko, head of the KGB secret service, accused the Opposition of planning to use the rally to stage a coup against Aleksander Lukashenko, the President, who has ruled the former Soviet republic since 1994.

"We will not allow the seizure of power under the guise of presidential elections," Mr Sukhorenko told a news conference.

"For those who take the risk of going out into the street and try to destabilise the situation, their actions will be qualified as terrorism" — a crime, he added, that can result in life in prison or the death penalty.

His stark warning set the stage for a dramatic showdown on Sunday that diplomats say could escalate into a confrontation between the West and Russia in Moscow’s debut year as President of the G8. The United States has branded Mr Lukashenko "Europe’s last dictator".

The EU said yesterday that it would tighten sanctions against Minsk if the elections were not seen to be free and fair. It demanded that Belarus release dozens of opposition activists and journalists who have been detained.

"The new wave of arrests of opposition leaders in Belarus over the last two days is completely unacceptable," said Benita Ferrero-Waldner, the EU External Relations Commissioner. "Such arrests have no place in the conduct of free and fair elections."

Josep Borrell, the European Parliament President, also expressed concern, noting that Belarus had refused to grant visas to a group of European lawmakers who wanted to monitor the election. The EU already imposes a visa ban on several Belarussian politicians.

Russia, however, is backing Mr Lukashenko in an attempt to stop another former Soviet state from moving out of its strategic sphere of influence and integrating with the European Union and Nato.

Mr Lukashenko, who has resurrected Soviet-style economic and political controls since coming to power, is certain to win a third five-year term in Sunday’s election. A Russian poll predicted yesterday that he would win 60 per cent of the vote.

But his main rival, Aleksander Milinkevich, says that the result has already been decided and is urging his supporters to rally in Minsk on Sunday evening.

Mr Milinkevich’s aides accused the KGB chief of using "scare tactics" and trying to justify the use of violence against protesters.

"This is absurd and nothing more than the agony of people trying to cling to power," said Anatoly Lebedko, a senior official in Mr Milinkevich’s campaign who was detained this week. "Thousands of people will take to the streets because they cannot be denied a right to choose," he predicted.

But he said that the authorities might organise explosions to justify a on the Opposition.

The KGB chief showed a video of a young man who said he had been ordered to detonate explosives at four schools in central Minsk on election day so that the Opposition could seize power in the ensuing confusion.

The man said that he had been given terrorist training by Arabs and American instructors at a camp in Georgia.