Three peace activists appeared today in the Wellington District Court charged with an attack on government spy base at Waihopai, near Blenheim, in April last year.

Adrian Leason, Peter Murnane and Sam Land allegedly committed two acts of willful damage - cutting a fence and slashing an inflatable dome covering a satellite dish - and a third of burglary by being in the yard belonging to the Government Communications Security Bureau (GCSB).

In his opening address, Crown prosecutor Hugh Boyd-Wilson said GCSB security staff found the three men sitting, having what appeared to be a prayer meeting beside one of the domes.

The three accused admitted they damaged the dome but said they were acting in self-defence.

The trial is set down for eight days.