EAST LONDON, February 13, 2014 (AFP) - Santos, 31, snatched four birdies on the front nine of the par-71 course in the Indian Ocean town and another five coming back.
He leads by two strokes from Denmark's Lucas Bjerregaard, Britons Richard Bland and Rhys Davies and South African Garth Mulroy.
Frenchman Gregory Bourdy and Scot David Drysdale are among six competitors on 65 and title-holder Darren Fichardt from South Africa is in a large group who carded 66s in good conditions.
Superb tee-to-green play by Santos, who won the 2012 Madeira Islands Open in his homeland, set up the birdie blitz.
"I did not miss a fairway and put the ball very close to the pin," said the golfer who also enjoys snooker and horse racing.
"That is the key to success on this course," added the golfer lying 89th on the European Tour rankings this season having earned 46,000 euros ($63,000).
"Today was definitely one of the rounds of my career," Santos said, recalling a round that twice reaped three consecutive birdies.
"To shoot minus nine you have to play awesome golf so I'm really pleased with every piece of my game. I played solidly and gave myself a lot of birdie chances."
Leading scores after first round of European Tour-Sunshine Tour co-sanctioned Africa Open golf tournament at par-71, 6,064-metre (6,632-yard) East London Golf Club Thursday (RSA unless noted):
62 - Ricardo Santos (POR)
64 - Lucas Bjerregaard (DEN), Richard Bland (ENG), Rhys Davies (WAL), Garth Mulroy
65 - Gregory Bourdy (FRA), Merrick Bremner, David Drysdale (SCO), John Hahn (USA), Brinson Paolini (USA), Fabrizio Zanotti (PAR)
66 - Thomas Aiken, Ulrich van den Berg, Heinrich Bruiners, Marco Crespi (ITA), Darren Fichardt, Oliver Fisher (ENG), Adam Gee (ENG), David Horsey (ENG), James Kingston, James Morrison (ENG), Matthew Nixon (ENG), Victor Riu (FRA), JJ Senekal, Patrik Sjoland (SWE), Brandon Stone, Mark Tullo (CHI), Simon Wakefield (ENG), Justin Walters