MADRID, Dec 15 (Reuters) - Spanish billionaire and Zara founder Amancio Ortega has bought a residential skyscraper in Seattle for $323 million, his private firm Pontegadea said on Thursday.

Ortega, the main shareholder of fashion giant Inditex and one of the world's 30 wealthiest entrepreneurs, signed the deal yesterday through his family office, Pontegadea added.

Kiara tower, located in Seattle's South Lake Union neighbourhood in the United States, has 461 luxury apartments and is 133 metres tall.

The purchase follows a $500-million investment in a 64-floor skyscraper of luxury apartments in New York's Financial District.

Pontegadea has focused on investing in real-estate assets worldwide and in Spain's energy infrastructure. Just this year, Ortega's investment vehicle also bought Royal Bank Plaza, a landmark skyscraper in Toronto, and one of the largest single-office buildings in Scotland. (Reporting by Corina Pons; Editing by Kirsten Donovan)