By Larry Fine
AUGUSTA, Georgia (Reuters) - Young American Jordan Spieth stretched his overnight lead to four strokes with a pair of birdies that took him to an impressive 10 under par early in the second round of the Masters on Friday.
The 21-year-old Spieth, whose opening round of eight-under 64 has been bettered only twice in the 79-year history of the Masters, birdied the par-five second and the par-four fifth on hot, humid day at Augusta National.
Spieth was threatening to make it a runaway, but others were mounting a chase, including big-hitting Australian Jason Day.
After a bogey on the first hole, Day made eagle-three at the second to reach six under par for the tournament.
Four-times major winner Ernie Els of South Africa got to six-under with a birdie at number two but gave a couple of shots back and stood at four under par after a bogey at the 10th.
His compatriot Louis Oosthuizen, who shot even-par 72 on Thursday, made four birdies in a flawless front nine to join Els at four-under.
One shot better at five under par were Spain's Sergio Garcia and American Charley Hoffman, both through two holes.
Tiger Woods, returning to competition after two months off to work on his game, produced a big roar with a birdie at the first.
Woods, who was erratic off the tee in shooting a one-over-par 73 in the opening round, used his three-wood off the tee at the first and was about 40 yards behind his playing partners in the fairway.
But the four-time winner rifled his approach shot to within eight feet of the hole in the back right pin placement and rolled in the putt for birdie to bring cheers from a packed gallery.
The former world number one, who has plummeted to 111th in the rankings, parred the next two holes to stand at level-par for the championship.
(Editing by Frank Pingue)