The Iranian opposition accused Tehran's Ministry of Information of ordering the killings. Tehran denied responsibility, even though one of the suspects later arrested, Kazem Darabi, was believed to be an agent in Berlin posing as a businessman.
Bernt Schmitbauer, Chancellor Helmut Kohl's security adviser, told a Berlin court on Thursday that the Iranian Information Minister, Hojatoleslam Ali Fallahyan, had asked the German authorities to halt or at least delay the trial of the four suspects while he was in Germany on a state visit last October. His demand was rejected, Mr Schmitbauer said.
He explained that Tehran was requesting reciprocity for earlier help in securing the release of German hostages in Lebanon. Previously both Bonn and Tehran had tried to play down the significance of Mr Fallahyan's demands.