Image copyright Reuters Image caption Heather Mack (right) was given a lighter sentence after giving birth to her daughter last month

A court in Indonesia has sentenced a US man to 18 years in jail for killing the mother of his girlfriend in Bali last year.

Tommy Schaefer's partner, 19-year-old Heather Mack, was also sentenced to 10 years for helping him with the killing.

The body of Sheila von Wiese-Mack, 62, was found stuffed inside a suitcase in the boot of a taxi at a luxury hotel in Bali last August.

The presiding judge described the killing as "sadistic".

Tommy Schaefer, 21, reportedly wept in court as he recounted how he hit Wiese-Mack, a wealthy American academic, with a fruit bowl during a row at a five-star resort.

He said he had been defending himself after Wiese-Mack became angry on learning that her daughter was pregnant, AP reports.

Image copyright AP Image caption Heather Mack's baby girl has been staying with her in Bali's notorious Kerobokan jail

Image copyright AP Image caption Police arrested the detained couple after finding them at a separate hotel in Bali

"The defendant's actions disturbed the public and can be considered sadistic," Judge Made Suweda said as he sentenced Schaefer. But the politeness and remorse shown by Schaefer during the trial meant he did not receive a heavier sentence, he added.

A three-judge panel said they gave Heather Mack a lighter sentence because she had recently given birth to a baby.

Reports say she and her mother had a troubled relationship, with police frequently called to their Chicago home.

After the violent episode at the hotel, the couple hid the body inside a suitcase which they then left inside the boot of a taxi. The driver alerted the police after the pair failed to return and he discovered blood on the suitcase.

The police later found them staying at another hotel in Bali.