Cycling ace Lance Armstrong brought Dublin's rush hour traffic to a halt today as more than 1,000 Irish cyclists - some still dressed in their corporate suits - joined the seven-times Tour de France winner for the impromptu ride announced on Twitter.

Armstrong, who threw down the gauntlet to New York, said: 'I don't think anyone can top Dublin now after this. NYC, what you got? London? Amsterdam? LA? Paris?"

"Thanks Dublin!! What a great park and a cool ride w/ all of you. I heard a 1000+ came out. I'm speechless. Gotta love a good bike ride!!"

Fans mobbed the cycling champion as they tried to book their place in history while the gardai (Irish police) tried to keep the starstruck traffic moving.

Fans rode everything from rickshaws to tricycles as the carnival of cycles made its way through Phoenix Park - which is also Europe's biggest urban park.

Speaking after the mass cycle, Armstrong said: "For me, I like to ride my bike anyway, so on a very simple level it's a very sunny, beautiful day in Dublin and I'd be going for a bike ride anyway.

"The story is, it's a great city and it's a great park. It's a great evening to go out - it's really sunny, but it wasn't just about the cycling here."

Armstrong stayed in Ireland after the Tour finished for a cancer conference hosted by his foundation LiveStrong.

Just last week, more than 300 people joined him on a ride in Paisley,


, when he sent a similar tweet.

But the Dublin Twitter ride was the biggest yet.

The cyclists were responding to today's tweet read: "Good morning Dublin. Who wants to ride this afternoon? I do. 5:30 pm @ the roundabout of Fountain Rd and Chesterfield Ave. See you there.."

Armstrong returned to competitive cycling this year after retiring in 2005. Since he was 25, he has undergone several treatments for cancer and is hailed by many for his good humor and encouragement for other cancer sufferers.