LEAD: Dibaba and Majewski repeat; Ennis delights; Jeter warns By John Bagratuni, dpa Eds: Adds day's other events, quotes; epa photos

London (dpa) - Tirunseh Dibaba of Ethiopia became the first back-to-back women‘s 10,000 metres champion and local heroine Jessica Ennis electrified the crowd with the biggest overnight points tally in heptathlon history as Olympic athletics got off to a flying start on Friday.

Tomasz Majewski of Poland got his second successive gold in men‘s shot put while world champion Carmelita Jeter of the US threw down the gauntlet to the Jamaican rivals in the women‘s 100m heats on day one of Olympic athletics.

Dibaba, the Beijing 2008 champion over 5,000m and 10,000m, ran away from her Kenyan rivals and stormed across the line in a 2012 world best 30 minutes 20.75 seconds and was already on her lap of honour before the final runners finished.

Sally Kipyego was second in 30:26.37 and fellow Kenyan Vivian Cheruiyot, who won the long distance double in Dibaba‘s absence at the 2011 worlds, took bronze in 30:30.44, both Kenyans running personal bests.

Majewski won the shot put with 21.89m over German world champion David Storl, who had 21.86m. Reese Hoffa of the United States got his first Olympic medal, a bronze with 21.23m, but the Americans have now failed to win gold in the event since 1996.

Majewski is the second man to repeat in the event, the only other being American Parry O‘Brien of the US in 1952 and 1956.

The 2009 world champion Ennis brought the house down from the start when she ran 12.54 seconds in the 100 metres hurdles, the fastest hurdles run ever in a heptathlon and a British record in the event as well.

She finished day one with an unprecedented 4,158 points after another personal best 22.83 in the 200m for a massive lead over Lithuanian Austra Skujte (3,974). Beijing 2008 gold medallist Natalia Dobrynska of Ukraine, whose husband and coach Dmitry Polyakov died in March of cancer, was 10th.

"I‘m knackered, I‘m so tired. It‘s a great way to end the first day. To lead after the first day makes me really happy," Ennis said.

Jeter led six runners undcer 11 seconds with 10.83 into Saturday‘s semi-finals, just two hundredths off her season best. Shelly-Ann Fraser-Pryce, who led a Jamaican sweep at the 2008 Games in Beijing and is the season leader with 10.70 seconds, also advanced handily from her heat in 11.00.

"I have no fear. It all comes down to who wants it most," she said. Both the semis and the final take place on Saturday.

The Americans definitely want to avenge their crushing 6-0 defeat in all men‘s and women‘s sprints (100m, 200m, 4x100m) against the Jamaicans in Beijing.

"Everyone is going to run their hearts out (Saturday)," a confident Jeter said.

The 100m started in the morning with a preliminary round minus the big stars, a new format to cope with an ever growing field.

They featured Afghanistan‘s only woman on the team, Tahmiha Kohistani, who ran a personal best 14.42, and Brunei‘s first ever woman at the Games, Maziah Mahusin, who had a national record 59.28 in the 400m heats.

"I am grateful to be the only female athlete competing for my country. It is a dream come true," Kohistani said.

World and Olympic champion Asbel Kiprop of Kenya reached the 1,500m semi-finals while the 2008 Olympic champion Irving Saladino of Panama fouled out in long jump qualifying.

"Today I don‘t know but the wind was everywhere in the stadium," Saladino said. "I‘m not disappointed. I was out for four months with surgery on my knee and only came back into training in April."

The atmosphere created by the fans drew warm praise, including from Lamine Diack, president of the ruling athletics body IAAF.

"It was wonderful to see a totally packed stadium for the first session of athletics," he said. "I do not remember the last time this happened and it shows the great affection Britain has for our sport."

The start of athletics also brought the Olympic flame back into the limelight. The flame had been burning quietly in the empty stadium since being lit at the opening ceremony a week ago, placed behind the finish line and not visible from the outside.

Athletics continues on Sunday when the first appearance of Usain Bolt in the 100m heats in the start of his 2008 title treble defence could easily outshine the day‘s medal events which apart from the 100m and the conclusion of the heptathlon are the men‘s 20km walk, long jump and 10,000m. dpa bag bwh hl