Budapest - Hungary's national chief of police said on Monday that the US Federal Bureau of Investigation (FBI) is helping in the hunt for the killers behind a recent spate of murders of members of the country's Roma community.

Gyorgy Bencze, speaking on Hungarian television's "Sunrise" programme, said the FBI will look at evidence collected by the Hungarian police and helping with the "profiling" of the killers.

"Our American colleagues have agreed to review the evidence collected by our staff in order to refine the criminal profiling," Bencze said.

Since November 2008, five Roma have been murdered in different parts of the country in what are thought to be linked, racially motivated attacks.

Justice Minister Tibor Draskovics said on Monday afternoon that he had personally requested the help of the FBI.

"Things are taking place that are unprecedented in Hungarian criminal history: a series of grave crimes, committed in a way that we have hitherto not seen," Draskovics said, as quoted by the state news agency MTI.

Bencze said that those committing the crimes must lead "irregular" lives, often disappearing for hours in the middle of the night, the state news agency MTI reported.

The police have put up a reward equivalent to 230,000 dollars for information identifying the murderers.

The police chief said that any accomplices to the attacks who were not directly involved in the killings could expect reduced sentences if they come forward and inform on the murderers.

Solving the Roma murders has become a "matter of honour" for the Hungarian police force, the police chief repeated.

A 100-strong team has been assigned to investigate 18 cases of attacks against Roma homes in the past 18 months using petrol bombs and, in several cases, guns.

Over a dozen attacks against Roma homes in Hungary since last summer alone have so far resulted in seven deaths, five of which are thought to be related.

A 43-year-old man and a 40-year-old woman were killed one night last November when petrol bombs were thrown into their homes amid a burst of gunfire in Nagycsecs in eastern Hungary.

Then, on February 22, a father and his five-year-old son were gunned down before dawn as they fled their burning home in Tatarszentgyorgy, 40 kilometres south of Budapest. The blaze is thought to have been started deliberately with petrol bombs.

Most recently, 54-year-old Jeno Koka was shot dead on April 22 as he left his home in Tiszalok in eastern Hungary to work a night shift at a local chemical plant.

Similarities between these murders, and other attacks in which the victims escaped alive, have led police to suspect that the crimes are linked.

The police have collected DNA samples from some of the crime scenes and have evidence which suggests the same weapon was used in several of the killings, Bencze said.

In all cases, the victims lived on the edge of villages, allowing their attackers to make a quick getaway.

Ethnic Roma, often referred to as gypsies, make up at least six per cent of Hungary's population of ten million. They are among Hungary's poorest citizens, often living in de facto segregation in rural communities.

Some 1,000 mourners, including politicians and Roma community leaders, attended Jeno Koka's funeral last week. (dpa)