LEAD: Busiest weekend of London Olympics as excitement grows By Anna Tomforde, dpa

London (dpa) - Olympic organizers promised an "extraordinary weekend" Friday as the London Games moved towards their sporting climax - fuelled by the thrill of competition and the mounting fervour of supporters.

"It‘s an electric atmosphere," said Debbie Jevans, the director of sport at organizing committee LOCOG.

Hours earlier, the athletics competition kicked off in the Olympic stadium Friday - a week after the spectacular opening ceremony in the same surroundings.

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

London was at the "start of an extraordinary weekend," said Jevans, as the marathon and swimming competitions moved to venues in central London.

"We are taking the Games on to the streets of London," she said.

This weekend, people across Britain have been called upon to celebrate the Games with parties and barbecues, while hundreds of thousands are expected to visit the Olympic Park in Stratford, east London.

However, the day started badly for some travellers Friday, as one of the main Underground (Tube) lines to Stratford was suspended in the morning rush-hour due to signal failure.

Passengers had to wait for up to an hour to board the high-speed Javelin train to the Olympic stadium from St Pancras Station, as queues snaked down the road outside the station.

Measures were also announced Friday to avoid overcrowding and congesting around the Olympic site.

On Friday and Saturday, access to Westfield shopping centre, a huge shopping mall on the edge of the park, will be restricted to accredited workers and people with tickets to the Olympic Park, including those who have booked a restaurant table at the complex. dpa aet bwh mis Author: Anna Tomforde