MADRID -- The brother-in-law of Spain's King Felipe VI has begun serving a nearly six-year sentence for fraud and tax evasion, Spanish prison authorities said Monday.

An official with the Interior Ministry's prison management division said Inaki Urdangarin arrived Monday morning at a prison near Avila, about 100 kilometres north of Madrid. The official spoke anonymously, in line with ministry rules.

Urdangarin, a 50-year-old former Olympic handball medal winner married to the king's sister, Cristina, is the closest person to the ruling Bourbon family to be imprisoned.

He was convicted to five years and 10 months in prison for embezzling about 6 million euros ($7 million) by exploiting his position in the royal family to obtain public contracts.

Cristina was fined 136,950 euros ($158,600) as a beneficiary of her husband's crimes.

The corruption scandal helped erode the image of the Spanish royal family and prompted the abdication in 2014 of Juan Carlos I, who ceded the throne to Felipe.

Urdangarin had been given five days to voluntarily turn himself in to begin serving his sentence after the Supreme Court rejected his appeal earlier this month.

The ministry official described the Brieva prison chosen by Urdangarin as a small facility with less than 100 inmates, most of them women.

The prison has a small module for men, but authorities could choose to send him elsewhere for security or internal organization reasons, the official said.

Spain's Royal House has said that it respects judicial decisions and King Felipe VI and Queen Letizia have not publicly commented on the result of the appeal.

The royal couple is on an official visit to the United States. On Monday they are scheduled to meet entrepreneurs and students in San Antonio, Texas, before travelling to Washington D.C. for a meeting Tuesday with President Donald Trump and first lady Melania Trump.