Stan Wawrinka of Switzerland serves to Thomaz Bellucci of Brazil during their men's singles match at the US Open in New York City on Wednesday (US time). Photo: CFP

Second-round action at the US Open began with a shock and ended with some late-night drama as men's third seed Stan Wawrinka barked at fans before shouting for joy at his 6-3, 6-4, 3-6, 7-6 (7/1) win over Thomaz Bellucci on Wednesday (US time).

The day got off to an explosive start with Chinese doubles specialist Peng Shuai upsetting fourth-seeded Agnieszka Radwanska of Poland 6-3, 6-4 and finished under the floodlights in the early morning hours with Wawrinka losing his cool and snapping at the rowdy crowd ­before escaping with a testy win.

After cruising through the opening two sets, Wawrinka had appeared set for a routine victory but the Swiss suddenly found himself in a titanic struggle with both the 95th-ranked Brazilian and some spectators.

In the third, Bellucci charged 5-1 ahead to keep the match alive and then secured an early break in the fourth as a frustrated Wawrinka muttered to himself.

With the tension building and the score locked at 5-5 after the Swiss had broken back in the sixth game, Wawrinka's mumblings turned to open rage as he screamed at one heckler to "shut up man."

The Australian Open champion would, however, quickly regain his composure as the set moved to a tiebreaker, which he dominated 7-1.

By contrast, Peng, half of this year's French Open women's doubles winning pair, quietly went about her business, taking 96 minutes to claim the biggest scalp of the tournament so far.

Radwanska, winner of the Montreal hard-court tuneup to the US Open and a semifinalist at this year's Australian Open, saved a match point in the ninth game to hold serve for 5-4 and fended off another in the next to briefly delay the upset.

Two former champions, fifth seed Maria Sharapova and ­19th-seeded Venus Williams ­delighted their center court audiences by flashing a little of their fashion style along with some on-court flair.

Williams, who claimed back-to-back US Open titles from 2000, kept pace with younger sister Serena by taming 78th-ranked Timea Bacsinszky of Switzerland 6-1, 6-4 to reach the third round for the first time in four years.

French Open champion Sharapova lost the first set to 95th-ranked Alexandra Dulgheru of Romania, but the five-time Grand Slam winner recovered to register a 4-6, 6-3, 6-2 victory and leave her fans smiling on a breezy Arthur Ashe Stadium court.

In another women's singles encounter, world No.2 Simona Halep of Romania beat the heat by hurrying past Jana Cepelova of Slovakia 6-2, 6-1.

Others advancing included sixth seed Angelique Kerber of Germany, ninth-seeded Serbian Jelena Jankovic and 10th-seeded former world No.1 Caroline Wozniacki of Denmark.

On the men's side, sixth-­seeded Czech Tomas Berdych dismissed 2001 champion Lleyton Hewitt of Australia 6-3, 6-4, 6-3 and seventh-seeded Bulgarian Grigor Dimitrov eased to a 6-2, 7-6, 6-2 victory over local wild card Ryan Harrison.