Prince Mohammed bin Salman's trip to Spain will come hot on the heels of a two-day official visit to France and after a tour lasting several weeks of the United States, Britain and Egypt, where the self-styled moderniser signed multimillion-dollar deals.

According to Spain's El Pais daily, he is due to sign a contract to buy five warships from Spain for two billion euros ($2.4 billion), as well as other bilateral agreements.

Rights groups have denounced the planned sale -- which has been under negotiation for two years -- saying the corvettes could be used in Saudi Arabia's military campaign in Yemen, which has killed thousands of civilians.

Spain and Saudi Arabia's royal families are very close due to King Felipe VI's father Juan Carlos, who was a close friend of the kingdom's late King Fahd, who reigned from 1982 to 2005, and is close to his brother King Salman.

Juan Carlos was credited with playing a decisive role in 2011 in helping a Spanish consortium win a contract worth 6.7 billion euros ($8.2 billion) to build a high-speed railway linking the holy cities of Mecca and Medina.

According to El Pais, Juan Carlos spent "a few days of rest" in Saudi Arabia just before Easter.

Felipe VI, meanwhile, paid an official visit there in January 2017.

Spain is currently the seventh largest arms exporter in the world.