London Olympic organisers were left red-faced on Tuesday when a huge clock in Trafalgar Square marking the countdown to the 2012 Games stopped just hours after being unveiled at a glitzy ceremony.

The steel digital clock measuring 6.5 metres tall and five metres long froze with 500 days, 7 hours, 6 minutes and 56 seconds to go before the start of the Games.

It had been unveiled on Monday by London Olympic organising committee (LOCOG) chairman Sebastian Coe and four British Olympic gold medallists, coinciding with 6.6 million Games tickets going on sale.

"We are obviously very disappointed that the clock has suffered this technical issue," a spokesman for Swiss watchmakers Omega said in a statement.

However, a LOCOG spokeswoman laughed off the malfunction, adding "it is not our clock."

Trafalgar Square is where Londoners gathered in 2005 to hear their city announced as winning bidders.

Omega said the clock, with its unique design for 2012, had been developed by experts and fully tested ahead of its launch.

"We are currently looking into why this happened and expect to have the clock functioning as normal as soon as possible," a spokesman added.

The clock's design draws heavily on the geometric lines of the 2012 logo and Greenwich Mean Time, organisers said.

Omega will also provide the timepieces for the Games, as they have done since 1932.

For more Bilingual News, please log on to our website at language.chinadaily.com.cn. For now, this has been ...

.