All eyes on swimming as Olympic tickets row rumbles on

American swimmer Ryan Lochte was gunning for his second gold medal of the Olympics on Monday as Games organisers aimed to quell concerns over empty seats by making thousands of tickets available.

Lochte, who got his Games campaign off to a flier on Saturday when he crushed compatriot and long-time rival Michael Phelps to win the 400m medley, suffered a reality check on Sunday in the United States' relay loss to France.

The 27-year-old will line up in the 200m freestyle final against China's Sun Yang, who will also be targeting his second gold of the Games after his win in the 400m freestyle on Saturday.

Phelps, meanwhile got his individual campaign back on track as he began the defence of his 200m butterfly crown.

The American eased through his heats early Monday to book his place in the semi-finals.

"I am pretty happy about this morning, that is all I need to be," said Phelps, who has held the 200m fly world record since 2001 and hasn't been beaten in a major international competition in the event over the same period.

Three other individual finals on Monday night promised explosive action: the men's and women's 100m backstroke and the women's 100m breaststroke.

Meanwhile the talk of the pooldeck on Monday continued to be the remarkable world record-breaking display of Chinese teenager Ye Shiwen in the 400m medley on Saturday, which has been greeted with scepticism in the British media.

Ye sought to dispel the clouds of suspicion surrounding her performances in London, denying the existence of doping in Chinese swimming.

"There is no problem with doping, the Chinese team has a firm policy so there is no problem with that," Ye said.

Monday's four swimming medals are among a total of 12 up for grabs across all competitions on Monday.

Host nation Great Britain, still awaiting their first gold of the Games, will be hoping diving star Tom Daley can challenge for honours in the 10m synchronised platform final where he competes with partner Peter Waterfield.

The first medals in artistic gymnastics will be decided with the men's team final event, where China and Japan will attempt to put poor qualifying displays behind them to challenge for gold.

Japan and China, the dominant force in Beijing in 2008, had been expected to fight it out for the major honours in London, but they were eclipsed by the United States, Russia and Britain on Saturday's opening day.

China were leading the medal table with six golds after Sunday's action but their hopes of adding to their tally early Monday suffered a setback when Zhu Qinan lost out in a 10m air rifle competition won by Romania's Alin Moldoveanu.

Away from the medals, Great Britain and Argentina will meet in a men's field hockey after recent tensions between the two nations on the 30th anniversary of the Falklands War.

At Wimbledon, Roger Federer and Serena Williams look to reach the last 16 of the tennis tournament.

Meanwhile under-fire London Olympic organisers (LOCOG) continued to face criticism over the banks of empty seats which have been seen across various venues since the Games got under way on Saturday.

Some 3,000 tickets from international sports federations were "put back in the pot" and sold to the public Sunday, LOCOG said amid growing public anger over empty seats.

Organisers have blamed the unfilled seats on accredited officials and members of the media who have failed to take up their reserved places.

LOCOG communications chief Jackie Brock-Doyle admitted however that the re-distribution of accredited seating was "not an exact science".