Pub manager Terence Chia told the 'Straits Times' newspaper he saw the couple taking off their clothes Saturday night at a staircase in a block of flats in Holland Village, known for its popular nightspots.

"Then, clothes in hand, they coolly walked in their flip-flops toward the market," he said, adding when the couple did a U-turn a sea of spectators was ready and poised with cameras.

"There were more than 200 people and everyone was taking pictures," the newspaper Wednesday quoted Chia as saying. "Even women were busy clicking and people were cheering, whistling and applauding like crazy."

Police said the couple, a Caucasian man and an ethnic Chinese woman in their 20s, had been arrested and released on bail. If convicted under Singapore law, they could face a fine of maximum fine of S$2000 ($1,330), up to 3 months in jail, or both.

Protests are rare in Singapore and only made legal last year in a designated area called "Speakers' Corner," modeled on London's Hyde Park.