Rights groups have criticised Saudi Arabia over the beheading of a young Sri Lankan domestic worker accused of killing an infant left in her care in 2005.

The Saudi Interior Ministry said in a statement run by the official SPA news agency that Rizana Nafeek was executed in the town of Dawadmy, near the capital Riyadh, on Wednesday morning.

Sri Lanka's Foreign Ministry said Nafeek was sentenced to death in 2007 after her Saudi employer accused her of killing his infant daughter while she was bottle-feeding.

"President Mahinda Rajapaksa made a personal appeal on two occasions immediately after the confirmation of the death sentence, and a few days ago to stop the execution and grant a pardon to Miss Rizana Nafeek," the Sri Lankan Foreign Ministry said in a statement.

London-based Rights organisation Amnesty International said the passport Nafeek used to enter Saudi Arabia in May 2005 stated she was born in February 1982, but her birth certificate states she was born six year later, which would have made her 17 at the time of the infant's death.

Condemning the execution, Nisha Varia, senior women's rights researcher for Human Rights Watch, said: "Saudi Arabia is one of just three countries that executes people for crimes they committed as children.

"In executing Rizana Nafeek, Saudi authorities demonstrated callous disregard for basic humanity as well as Saudi Arabia's international legal obligations."

Saudi Arabia follows the strict Wahhabi school of Islam and applies Islamic law. Judges base decisions on their own interpretation of the law rather than on a written legal code or on precedent.

Saudi households are highly dependent on domestic workers from African and South Asian countries.

In a statement before the execution, Amnesty International said that it appeared Nafeek had no access to lawyers either during her pre-trial interrogation or at her trial in 2007.

"It appears that she was herself a child at the time and there are real concerns about the fairness of her trial," Philip Luther, Amnesty International's Middle East and North Africa programme director, said the day before the execution.