* De Lucia helped legitimise flamenco in Spain, worldwide
* Said "learned guitar like child learns to speak"
* Teamed up with Chick Corea, Al Di Meola, other musicians (Adds details on death, clarifies time of death as Tuesday in Mexico)
By Raquel Castillo and Elisabeth O'Leary
MADRID, Feb 26 (Reuters) - Paco de Lucia, the influential Spanish guitarist who vastly expanded the international audience for flamenco and merged it with other musical styles, died suddenly of a heart attack on Tuesday evening in Mexico.
The 66-year-old virtuoso, as happy playing seemingly impossible syncopated flamenco rhythms as he was improvising jazz or classical guitar, helped to legitimise flamenco in Spain itself at a time when it was shunned by the mainstream.
"I learned the guitar like a child learns to speak," the guitarist said in a 2012 documentary.
Born Francisco Sanchez Gomez, he became famous in the 1970s after recording the bestselling album "Entre Dos Aguas", becoming the first flamenco musician to perform at Madrid's opera house Teatro Real in 1975.
Paco's albums such as "El Duende Flamenco de Paco de Lucia" and "Almoraima" reinvented traditional flamenco.
He toured extensively with well-known international artists and played with the likes of Carlos Santana and Al Di Meola, happy to expand flamenco rhythms into jazz, although that upset flamenco purists.
"It has been said, and rightly so, that Paco de Lucia has never been surpassed by anyone and guitar playing today would not be understood without his revolutionary figure," Spain's arts association SGAE said in a statement.
De Lucia went on to record flamenco jazz fusion with Di Meola and John McLaughlin in a series of now legendary concerts, and also recorded with Chick Corea.
He was highly acclaimed after playing Joaquin de Rodrigo's "Concierto de Aranjuez" at London's Festival Hall in 1991, attended by the composer himself, and considered one of the best interpretations of the piece.
De Lucia memorised the piece by ear as he did not read music and gave it a distinctive flamenco flavour.
"With the guitar I've suffered a great deal, but when I've had a good time, the suffering seemed worthwhile," he said in the documentary.
He also formed a partnership in the 1970s with singer Camaron de la Isla which played a large part in creating the New Flamenco movement.
A spokesman for the city hall in Algeciras, where de Lucia was born, confirmed his death on Wednesday and said the city had decreed two days of official mourning.
Mexican authorities later said he had died on Tuesday at 7.15 local time while on holiday with his family on the Mexican Caribbean, after he was taken to a hospital complaining of pains in his chest. (Additional reporting by Rodrigo de Miguel and Tracy Rucinski in Madrid and Isela Serrano in Cancun, Mexico; Editing by Fiona Ortiz, Angus MacSwan, Michael Roddy and Sonya Hepinstall)