Comeback queen Justine Henin issued an ominous warning to her rivals at the Australian Open by knocking out Russian fifth seed Elena Dementieva 7-5, 7-6 in the second round on Wednesday.

In a pulsating, high-quality contest, 2004 champion Henin was the first to strike, breaking Dementieva's serve at 5-5 and sealing the first set on her third set point at Rod Laver Arena.

Dementieva hit back in the second, breaking Henin at 6-5 to force a tiebreak, but then gifted her match point with a netted drop-shot, allowing the Belgian to seal it 8-6 with a volley.

Henin's third-round opponent will be another Russian, 27th seed Alisa Kleybanova, who earlier beat Sorana Cirstea 6-4, 6-3.