Budapest - A Roma couple were killed in their sleep when a hand grenade was thrown through the window of their house in southern Hungary, authorities said Wednesday.

A 37-year-old man and his 31-year-old wife died in the blast late Tuesday in the town of Pecs. Two of their three children were slightly injured.

Police were quick to dismiss the idea that the attack was racially motivated. The case was probably a Mafia-style revenge killing, county police spokesman Peter Zsobrak said on Hungarian television.

He said police had found no evidence of a link to a November 3 attack in north-eastern Hungary that left two Roma dead.

In that case, a man and a woman died in a hail of gunfire after petrol bombs were thrown into two houses in the village of Nagycsecse.

Roma, or Gypsies, make up about 7 per cent of Hungary's population of 10 million.

Anti-Gypsy sentiment has risen over the past two years, most visibly with marches through Roma communities by the extreme nationalist Hungarian Guard, a uniformed paramilitary organization. (dpa)