Image caption Organisers expect 1 million extra visitors to London to make 3 million journeys on public transport

London's transport network is facing its first major test on the first working day of the Olympics.

Transport chiefs say the morning rush hour went relatively well. The evening peak will provide a further test.

Meanwhile, Tom Daley and diving partner Pete Waterfield, and the men's gymnastics team are among those aiming to win medals for Team GB.

And London Mayor Boris Johnson has told BBC News that more tickets will go on sale to the public to fill empty seats.

And Labour has called for urgent action to make sure empty seats at the Games are filled by sports fans.

At some venues, seats in the accredited "Olympic family" areas - reserved for groups including officials, sports federations, athletes, journalists and sponsors - have remained empty.

"We've got to get people into those seats today, tomorrow and the next day," shadow Olympics minister Tessa Jowell told BBC's Radio 4's Today programme.

But she praised an announcement by Lord Coe - who has said Olympics venues are "stuffed" with sports fans - that some empty seats would be filled by servicemen and women, as well as local students and teachers.

'Working hard'

Transport for London's Games transport director Mark Evers said the network was working well on Monday morning and that 3,500 back office staff were out and about fielding questions from travellers.

Analysis It has not been such a manic Monday so far. London workers seem to have heeded warnings that extra restrictions and Games Lanes, combined with spectator congestion might result in nightmare commutes, and have changed their patterns. Roads seem no more jammed than normal, train and tube lines are running well. Even at London Bridge, where passengers have their own Olympic time trial today - diverted away from the usual routes in case of overcrowding - there were no complaints. But this is a marathon, not a sprint. Six platforms at London Bridge will be exit only this evening as 50,000 equestrian spectators all head home from Greenwich Park during the evening peak. And the crunch transport test comes on Friday - the first full day of athletics in Stratford's 80,000-seat Olympic stadium.

"Nothing can prepare you fully for the Olympics but we're working very hard to make sure that we both get people to the Games but also make sure that London keeps moving as well," he told BBC News.

London Bridge is expected to be particularly busy later with thousands of spectators heading to the Olympic Park and equestrian events in Greenwich.

But Steve McNamara, general secretary of the Licensed Taxi Drivers' Association - representing London cabbies - complained of "chaos" on London's roads as a result of 30 miles of Games Lanes for the use of the Olympic family.

He told BBC News "tens of thousands of Londoners are stuck in gridlock traffic" while Games Lanes were "completely empty".

Olympic organisers expect 1 million extra visitors to London to make some 3 million journeys on public transport - on top of the city's daily staple 12m public transport journeys.

Those intending to travel in the city are warned to leave extra time for their journeys and plan ahead by using the Games' dedicated transport advice website .

Britons travelling to the Olympics will hope for more medals after cyclist Lizzie Armitstead and swimmer Rebecca Adlington won Team GB's first two on Sunday.

Armitstead won silver in the 140-kilometre road race and swimmer Rebecca Adlington won bronze in the 400m freestyle - following her gold in the same event in Beijing in 2008.

Adlington will begin her quest to defend her Olympic 800m freestyle title in heats on Thursday morning before Friday night's final.

Tom Daley and Pete Waterfield will hope to follow in their footsteps with medals in the men's synchronised 10m platform final, which begins at 14:55 BST.

And Britain's men, who have made history after qualifying in third place for the gymnastics team final - ahead of Olympic and world champions China - will compete at 16:25 BST.

Meanwhile, organisers say locks have been changed at Wembley Stadium and insist security has not been compromised by the loss of a set of security keys.

The keys were being used by police officers during searches of the stadium ahead of the Games last week.

BBC home affairs correspondent Danny Shaw says it was an embarrassing blunder that may have been the fault of the police.

The Met Police said key areas of the venue were immediately secured and there had been no "evidence of criminal offences".

In other Olympic developments: