The Agusta affair has implicated some of Belgium's most senior political figures in a scandal which extends from bribery to money-laundering, forgery and possibly even murder.

BBC Europe Correspondent David Eades

Apart from Willy Claes, two former deputy prime ministers are also on trial for their alleged role in securing huge government contracts for defence firms at the end of the 1980s, in return for substantial contributions to Socialist Party funds.

One involved the Italian manufacturer, Agusta, in a deal to provide helicopters to the Belgian army.

Another contract, to modernise fighter planes, went to a subsidiary of the French firm, Dassault.

As economics minister at the time, Mr Claes signed both contracts, but flatly denies any knowledge of payments in return amounting to around $2m.

Until 1989, private contributions to political parties were legal.

They have since been banned, so the prosecution must prove the money was linked directly to the contracts, not simply a gift.

Mystery death

Despite the allegations, the socialists remain in the coalition government.

Yet whatever the outcome of this trial, their problems are unlikely to disappear.

Details of the Agusta payments only emerged during investigations into the murder in 1989 of Andre Cools, another leading socialist.