BARCELONA (Reuters) - Juan Antonio Samaranch was given a send-off resembling a state funeral in his native Barcelona on Thursday, a day after the former International Olympic Committee (IOC) president died at the age of 89.

King Juan Carlos and his family, current IOC president Jacques Rogge and high-profile figures from Spanish sport and politics were among the mourners.

Rafael Nadal, the world's number three tennis player, helped carry the coffin to the city cathedral.

The casket, draped in the Olympic flag, had earlier been placed in the chapel at the Catalan regional government's palace and hundreds of people filed past to pay their respects to the man who brought the Olympic Games to the port city in 1992.

"I came here above all to support the (Samaranch) family and show appreciation for everything he did for our sport," Mallorca-born Nadal said.

"He was able to revolutionize sport, until he became one of the most important people in the international Olympic movement," the 23-year-old added. "He will always stay in our thoughts."

Samaranch was admitted to the Quiron clinic in Barcelona on Sunday with acute heart problems and passed away on Wednesday after suffering "cardio-respiratory failure."

After steering the Olympic movement through two turbulent decades, marked by political boycotts, bribery and drug scandals and a greater emphasis on commercialism, he was appointed honorary life president of the IOC when he stepped down as president in 2001.

"I can say today that Samaranch was the most influential IOC leader since (founder) Pierre de Coubertain," Rogge said in a televised speech at the Catalan government palace.

"Samaranch changed everything and made the Olympic Games what they are today."

Samaranch will be buried at the cemetery on the Montjuic hill near the stadium that was used for the 1992 Games.

(Additional reporting by Emma Pinedo in Madrid; Writing by Iain Rogers in Madrid, editing by Ed Osmond)