With 35 per cent of the vote counted, Robert Kocharian had 38 per cent to the former Communist leader Karen Demirchian's 27 per cent. Turnout in Monday's national election was high, with voters discontented over economic decline.
The official Communist Party candidate, Sergei Badalian, had 17 per cent of the vote. As none of the candidates was likely to get an outright majority, a run-off between the top two is likely on 30 March.
The results are likely to be contested. Seven of the 12 candidates were alleging fraud - the same accusation Armenians made against their former president, Levon Ter-Petrosian, whose resignation last month opened the way for Monday's vote.