SEOUL - Samsung Electronics Co said on Monday it would unveil the third-generation of its flagship smartphone Galaxy S on May 3 in London, banking on a heavy marketing campaign heading into the summer Olympics in the city.

Samsung became the world's top smartphone maker last year on the back of strong sales of Galaxy lineups and the latest edition comes after it released Galaxy S II in late April last year.

The South Korean firm sold over 40 million Galaxy smartphones since the model was released in June 2010.

Samsung, which dominates in the top end of smartphone market along with Apple Inc , estimated earlier this month that its first-quarter operating profit would hit a record 5.8 trillion Korean won thanks to strong sales of Galaxy series smartphones.

Its current sponsorship deal with the International Olympics Committee runs out in 2016. It has said its market share in China doubled after the 2008 Beijing Olympics.

(Reporting by Miyoung Kim; Editing by Kim Coghill)