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Spanish opera star Placido Domingo said Wednesday he expected to feel "much better soon" after treatment for a blockage in his lung which forced him to cancel a string of concerts in Madrid.

"I will be feeling much better soon. Thank you all from the bottom of my heart," he told his fans in a message on the social network Facebook.

The 72-year-old, popularly known for his "Three Tenors" performances with Jose Carreras and the late Luciano Pavarotti, was admitted to hospital in the Spanish capital on Monday.

"He is being successfully treated for a pulmonary embolism," a blockage of an artery of the lungs, and is expected to make a full recovery, his US-based agent Nancy Seltzer said in a statement.

She said the embolism was caused by deep vein thrombosis -- a condition in which a clot forms in a deep vein, often in a leg.

"He will be forced to rest for three to four weeks. His exact return to his performing engagements remains subject to how fast he can heal and regain his characteristic strength."

The Grammy-winning singer had to cancel five performances in Daniel Catan's opera "Il Postino", due to begin at the Teatro Real in Madrid on July 17.

He also bowed out of a concert he was due to conduct on Madrid's Plaza Mayor square on July 21, the agent said.

"The saddest part of it all is being in my own city and unable to perform for Madrid's public," Domingo said in his statement on Wednesday.

Born in Madrid, Domingo moved to Mexico as a child with his parents, who ran a company that performed zarzuela, the traditional Spanish operetta form.

His repertoire encompasses 140 stage roles -- a number unmatched by any other celebrated tenor in history.