MELBOURNE, Jan. 17 (Xinhua) -- World No. 1 and defending Australian Open champion Simona Halep survived a second round scare at this year's tournament on Thursday, after dropping the second set to 20-year-old American challenger Sofia Kenin.

Off to a fine start, the Romanian broke early and took the first set 6-3, but a spirited fightback from the world No. 37, who recently claimed her first WTA title at the Hobart International earlier this month, saw Halep with her back against the wall.

Down 2-4 in the third set, Halep managed to win the next four consecutive games, snatching the victory from Kenin and booking her place in the next stage of the tournament with final scores of 6-3, 6-7 (5) 6-4.

No stranger to difficult marathon contests in the early rounds, at last year's Australian Open Halep won the longest women's match in the tournament's history against Lauren Davis, in a time of around four hours.

"I've no idea how I won tonight," Halep said after the match.

"It's so tough to explain what happened on court, but it was a very tough one against an amazing player."

"It was really difficult to stay there for every ball, to run so much. I got a little bit injured in the second set but I just fought, because I wanted to win and to come back here."

"Hopefully in the next round, I'll play better and make a better match," she added.

Halep will now take on Venus Williams in the third round.