Thousands of couples across Asia swamped marriage registries and held mass weddings on Friday, believing that the quirk of the calendar makes 11/11/11 the most auspicious date in a century.

In China, the world's most populous country, registries were packed with couples wanting to wed on the date that has been recognised as an unofficial "singles' day" since the 1990s because it is made up entirely of the number one.

"We are getting married on the day of 'six ones'. We will no longer be single on the once-in-a-century singles' day," said Shanghai hotel manager Li Xue, 26, who brought forward her wedding plans after realising the date's significance.

Traditionally seen in China as a good day to marry and leave the single life behind, this year's November 11 is viewed as particularly special because the year also ends in the number 11.

In the commercial capital Shanghai alone, nearly 5,000 couples got married, while in the eastern Chinese city of Jining, 68 couples tied the knot together at a mass wedding.

In Vietnam, 80 couples planned to get hitched at a mass wedding to be held in Ho Chi Minh city -- the largest ever for the country's commercial capital.

One of Hong Kong's leading feng shui masters, Mak Ling Ling, said November 11 was a good day for marriages, but that it was also auspicious for other new beginnings, such as moving house and groundbreaking ceremonies.

"It's a good day from a Chinese geomancy perspective, not just because of the numbers 11/11/11 which signify eternal love," said Mak, an author and television personality.

Some people also believe the date is lucky because if you add the numbers in the date -- six times one plus 2 -- the total is eight, traditionally a lucky number because it sounds like part of the Chinese phrase for "get rich".

"We Chinese people do believe in numbers. It may be superstitious, but I think it's great to have your favourite numbers on your most important day," said He Ying, who was also marrying in Shanghai on Friday.

In South Korea, hospital officials moved to debunk reports that the number of women seeking Caesarian operations on the day had jumped as mothers sought to give their children that special birth date.

But in Singapore, whose population is dominated by ethnic Chinese, the Registry of Marriages predicted a high turnout, with 574 bookings for the day -- five times the typical number.

Wedding planners said the date was an extremely popular one for couples wanting to get hitched in the island nation, but November 20 this year will even be bigger, since 20/11/2011 is an exact repetition of the numbers.

"We did have, definitely, significantly more enquiries for this date," said Clarice Hee of wedding planner firm Eternally Yours, but she added the number would be eclipsed by November 20.

Australians usually mark November 11 as Remembrance Day, with ceremonies for the nation's war dead, but this year there was a spike in weddings.

"I had a lot of interest for the eleventh of the eleventh of the eleventh. Clients were specific, they even wanted to be saying their vows at 11 minutes past 11," Queensland-based wedding celebrant Renee Wilkins said.

However, Hong Kong feng shui master Mak warned that marrying on the lucky date would not necessarily guarantee happiness.

"It's a good start, definitely, but whether or not they will end up in divorce, it depends on how the couples maintain their marriage," she said.