A teenage boy has married a 73-year-old woman after they threatened double suicide if officials blocked the wedding.

Selamet Riyadi, 15, began a relationship with his elderly neighbour Rohaya Binti Kiagus Muhammad Jakfar after she cared for him while he was suffering from malaria.

Authorities in their remote village in Sumatra, Indonesia, allowed the ceremony despite the legal age for men to marry in the country being 19.

"Selamet is too young to marry but we married them anyway because he threatened to commit suicide," village chief Cik Ani, told the Agence France Presse news agency.

"Since the boy is an underage, we have decided to carry out the marriage privately," he said, adding officials also wanted the couple to "avoid the sin of adultery".

Selamet's father died several years ago and he was reportedly not properly cared for by his mother, who has remarried.

His bride has been married twice before and has at least one child.

The teenager's wedding took place in the remote Karang Endah village over the weekend. It sparked national interest after footage of the ceremony emerged online.

Indonesia's social affairs minister criticised the union, which she said was unofficial as the groom was underage.

Khofifah Indar Parawansa told The Jakarta Post: "A team from the Social Affairs Ministry checked and found that they held an unofficial wedding, thus they don't have a marriage deed.

"It's not possible for them to marry in a KUA [religious affairs office], because the groom is still underage."

She added: "The law also says that marriage registration officials should not assist in a marriage when they know that there's a violation of the minimum age requirement to marry."