Austrian authorities said three people have been arrested over the deaths of 71 refugees whose decomposing bodies were found inside a lorry not far from the Hungarian border. Police said 59 men, eight women and four children, including a girl of between one and two years of age and an eight-year-old boy, lost their lives.

They said four European arrest warrants were issued in relation to the case, with three people, all Bulgarian nationals, already arrested in Hungary.

The victims are believed to be Syrians, for a Syrian travel document was found inside the truck, a police spokesperson said, adding that the investigation is still ongoing but they could rule out there were any African on inside the truck.

The vehicle was found parked on the hard shoulder of a highway near the eastern town of Parndorf, not far from the border with Hungary and Slovakia on 27 August as EU representatives met with their non-EU Balkan counterparts in Vienna to discuss the migrant crisis.

It formerly belonged to a Slovakian food company but had Hungarian licence plates. Authorities said it was now registered to a Romanian citizen of Lebanese descent living in central Hungary. The man was among the three suspects held and police said they have reason to believe he was also the driver "at some point".

Hungarian authorities arrested a total of seven people connected to the case but Austrian police said the focus of their probe remains on the three Bulgarian nationals.

The lorry was spotted by staff at a service station who became suspicious when it had not moved for a long time. Police were called and they made the grim discovery. Blood was said to be dripping from the vehicle. Police said the refugees had been dead for at least 24 hours, as some corpses appeared to be partially decomposed in the summer heat.

A post mortem examination is to be carried out to determine what caused the deaths, but Austria interior minister Johanna Mikl-Leitner suggested they died of suffocation. She called the incident a "Wakeup call" for Europe. "Our shock and empathy with the families of the victims won't suffice, we need to act," she said.