US break 27-year-old relay world record

The United States fired a shot across Jamaica's bows in the ongoing battle for global sprint supremacy by obliterating the 27-year-old world record in the Olympic women's 4x100m relay final on Friday night.

A team including London 200m gold medallist Allyson Felix and reigning 100m world champion Carmelita Jeter proved too strong for an equally star-studded Jamaican lineup who had two-time Olympic 100m champion Shelly-Ann Fraser-Pryce running the lead-off leg.

But the Jamaicans were never really in the hunt, with Jeter motoring away from Kerron Stewart in the final straight as the US quartet clocked a time of 40.82 seconds.

The team, which also included Tianna Madison and Bianca Knight, smashed the old record of 41.37 set by East Germany way back in 1985 at the World Cup in Canberra.

There was no sign of the baton change fragility the Americans have sometimes shown in the past.

"I knew that these girls were going to run their hearts out," said Jeter, who gestured at the time clock as soon as she crossed the line.

"I knew we were running fast. I was already pointing at the clock, saying 'there it is'.

"There was a cloud hanging over us, with people saying 'they can't do this, they're going to drop the stick' but we did it."

Frenchman Renaud Lavillenie set an Olympic record of 5.97m to win the men's pole vault, adding one cemtimetre to the mark Australian Steve Hooker set four years ago in Beijing.

Lavillenie ended the competition with two unsuccessful attempts at 6.07m, which would have moved him to second place on the alltime list behind the legendary Sergey Bubka.

Bjorn Otto (5.91m) claimed the silver medal on countback ahead of fellow German Raphael Holzdeppe.

But it was a disappointing night for Hooker, who exited the final without registering a single clearance.

Meseret Defar ended fellow Ethiopian Tirunesh Dibaba's bid for a remarkable Olympic distance double-double in London.

Dibaba had won the 5000m and 10,000m four years ago in Beijing and looked unstoppable in defending the longer title on the opening day of the athletics program in London.

But Defar found a way to stop Dibaba, running by her more famous countrywoman in the final straight to win in 15 minutes 04.25 seconds.

Vivian Cheruiyot of Kenya claimed the bronze, with Dibaba having to settle for a rare bronze.

It was a second Olympic title for the 28-year-old Defar who won the 5000m title eight years ago in Athens.

Once she crossed the line, Defar produced a religious image of a virgin and child to show to the cameras before breaking down, sobbing into the picture.

The Bahamas upset an under-strength US lineup missing the injured Lashawn Merritt and Manteo Mitchell - who broke his leg in the semis - in the men's 4x400m final.

The Americans had won this event at the past seven Games but had to cede their crown when Ramon Miller mowed down Angelo Taylor on the final lap.

The Bahamas clocked a winning time of 2:56.72.

Double-amputee runner Oscar Pistorius ran the anchor leg for South Africa, who finished eighth, having been added to the final on appeal.

Drug cheat Asli Cakir Alptekin led a Turkish one-two in the women's 1500m in 4:10.23 ahead of Gamze Bulut and Bahrain's Maryam Yusuf Jamal.

Cakir Alptekin returned to the sport after serving a two-year drug ban following a positive test at the 2004 world junior championships.

Russian Tatyana Lysenko won the women's hammer throw with an Olympic record throw of 78.18m ahead of Poland's Anita Wlodarczyk and Betty Heidler of Germany.

A Jamaican team resting Bolt still clocked the fourth-fastest time ever of 37.04 in the heats of the 4x100m.

Bolt will be back for Saturday's final where he'll be chasing his third gold medal of the Games to match the treble he pocketed four years ago in Beijing.