A Mauritanian court has jailed three people for between 10 and 20 years for slavery, a crime that critics say has gone widely unpunished in the conservative West African country.A judicial source said a special court in the northwest town of Nouadhibou this week handed down 20-year terms to a man named Saleck Ould Oumar, who died before the case concluded, and his son.They were accused of "reducing to slavery" a family, two of whom were children.It also gave a 10-year term to a woman named Ar-Rabiaa Mint Hammadi, accused of enslaving three sisters.The defendant said she did not have any children and treated one of the sisters as her own offspring, "satisfying all her needs, but not feeling the need to pay her a given salary" for her work.This argument was rejected by the public prosecutor, who said "there are not two kinds slavery - gentle and harsh - slavery is a crime," the source said.Officially, slavery was outlawed in Mauritania in 1981 but campaigners say it remains a bastion of the practice.A hereditary system of servitude forces members of the "slave" caste to work without pay as cattle herders and domestic servants, despite the official ban.In 2015, Mauritania adopted a new law declaring slavery a "crime against humanity" punishable by up to 20 years in jail, compared with a maximum of 10 years previously.It also set up three specialised anti-slavery tribunals in Nouadhibou, the capital Noukachott and in the southeastern town of Nema.Prosecutions, though, have been rare. The court in Nema pronounced five-year terms against two men in May 2016.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. Campaigners praised the latest rulings, saying they held out hope for ending the logjam."The trial went ahead smoothly, respecting the rules, and the law has been upheld," said a lawyer for the victims, El-Id Ould Mohameden, who added "there is now hope for normalising the humanitarian situation in the country."The head of an anti-slavery association SOS Esclavage, Boubacar Ould Messaoud, agreed.Several similar cases "have been pending for several years" at the three courts, he told AFP, adding that he had received assurances from the authorities that "these cases will be reactivated."A report by Amnesty International, published on March 21 and citing estimates by specialised organisations, said as many as 43 000 people - one percent of the population - were still living in slavery in Mauritania in 2016."Police, prosecutors and the judiciary failed to respond adequately to reported cases of exploitation, to identify victims or punish suspected perpetrators," it said, estimating that the courts had received 47 cases for investigation involving 53 suspects.