Police in Italy are hunting the relatives of a Pakistani girl who they think was strangled to death and buried in a shallow grave in a so-called honour killing.

Saman Abbas, 18, has been missing since May 1 when she was last seen on CCTV at a farm near the city of Reggio Emilia, central Italy, where father Shabbar, 46, worked.

Police says Shabbar conspired with Saman's mother Nazia Shaheen, 47, uncle Hasnain Danish, 33, and cousins Nomanulhaq Nomanulahq and Ijaz Ikram, 33 and 28, to kill her and bury her body behind the farm before fleeing the country.

Investigators believe the relatives hatched the plot after Saman refused to enter into an arranged marriage with a cousin in Pakistan because she had a boyfriend in Italy and wanted to live a 'Western' lifestyle.

Ijaz has since been arrested in France on suspicion of murder and extradited back to Italy. Shabbar and Nazia are in Pakistan and have denied murder of their daughter.

The whereabouts of Hasnain - who prosecutors say masterminded the killing - and Nomanulhaq are unknown.

Prosecutors say the case dates back to autumn last year, when the family tried to force Saman into an arranged marriage in her native Pakistan.

Saman fled the family home after an argument and since October had been living in a refuge run by social services, fearing for her safety.

But she returned home on April 11 this year, apparently to collect identity documents - though it is unclear exactly why she needed them.

Police believe that by April 26 the family had begun preparing for her murder.

That is the date on which uncle Hasnain is alleged to have bought plane tickets for her parents to fly back to Pakistan, prosecutors say.

Then, on the evening of April 29, CCTV captured three men who police say are Hasnain, Nomanulhaq and Ijaz walking into fields behind the farm around 7.30pm.

The trio are carrying two shovels, a bucket, and a blue bag with a crowbar in it. They are gone for around two hours, before returning home.

The following day, Saman reportedly overheard a conversation between her relatives, and told her boyfriend that they were planning her murder.

Saman's boyfriend, who was not at the property, told Italian newspaper Gazzetta di Reggio Emiliano that she texted him saying she had overheard her uncle remark that murder is 'the only solution' for girls who disobey Pakistan's strict honour codes.

The boyfriend was instructed to contact police in two days if she hadn't messaged him.

The boyfriend said he tried to reassure her, but she said: 'I'm not confident.'

Police say more CCTV footage - which hasn't been published - then shows parents Shabbar and Nazia walking their daughter into the fields behind the farm at nine minutes past midnight on May 1.

The pair return just 13 minutes later, with father Shabbar carrying a backpack that Saman had previously been wearing.

Police believe the parents handed Saman over to her uncle and cousins who were waiting in the fields and who killed her and buried her body somewhere on the farm.

The family then left home - Shabbas and Nazia for Pakistan, ostensibly to visit a sick relative, while Ijaz headed into Europe.

When police called at the family farm looking for Saman on May 5, they found Hasnain and Saman's 16-year-old brother at home, who explained that the rest of the family had gone to Pakistan to see a sick relative, Corriere reports.

Then the pair also vanished. On May 9 they were stopped at the Italian border with France because the brother was not carrying his identity documents.

Those men should be flogged with a thick strip of bacon.

A fate worse than death.