Spanish police on Monday said they had arrested a Pakistani man in connection with the killing of three siblings in their 70s, over debts reportedly linked to an online romance scam.

The suspect turned himself in on Sunday, “admitting his involvement in incidents related to the triple murder in a house in Morata de Tajuna”, a police statement said.

Judicial sources said the suspect had previously been convicted for attacking one of the sisters with a hammer a year ago.

Police had on Thursday found the three bodies, which were partially burnt inside their home in the village some 35 kilometres (20 miles) southeast of Madrid.

Neighbours raised the alarm after not seeing the two sisters and their disabled brother for some time, with police saying their deaths were being treated as murder over a suspected debt.

Police on Monday said the man, referred to only as D.H.F.C, was the “main suspect” in the case as he had “previously injured one of the female victims last year”, with the courts confirming his arrest and conviction.

Quoting residents, Spanish media said the tragedy was likely linked to a fake online love affair, with the two sisters embarking on what they thought was a long-distance relationship with two apparent US servicemen.

They were led to believe one had died and that the other needed money so that he could send them a multi-million-euro inheritance, causing the sisters to rack up huge debts.

Initially, they began borrowing money from neighbours.

During that time, the suspect had reportedly lent the sisters at least 50,000 euros ($55,000), which they had never repaid, prompting his violent attack on one of the sisters.

According to a statement from the Madrid region’s top court, the suspect was arrested in February 2023 at their house, where he was living as a tenant.

According to the sentence, he hit the victim “on the head, at least three times, with a hammer” Then when she fell to the floor, he kicked her.

He was held in pre-trial detention until his case came to court in September when he was handed two years behind bars, slapped with a 2,900 euro ($3,150) fine and banned from being within 500 metres (1,600 feet) of the victim for two years and six months.

But under Spanish law, anyone receiving a jail term of up to two years on a first offence automatically has their sentence suspended, so he was released after agreeing to pay the compensation, the statement said.

Police initially said the suspect was 43, but court records showed that he was 42.

When they called the police last week, neighbours said they hadn’t seen the siblings since before Christmas.

Speaking to Spanish media, they said the sister had repeatedly asked to borrow large sums of money, refusing to believe it was a scam and saying they would pay it back when they got the seven-million-euro ($7.6 million) inheritance payout.

“They weren’t asking for 100 euros or 20, they were asking you for 5,000 or 6,000 euros,” one neighbour had told state-owned broadcaster TVE on Friday.

Police did not comment on those reports.