Thousands of athletes and officials gathered in Incheon on Wednesday as the clock ticked down to Asia's biggest sports spectacular and organisers fretted over low ticket sales.

Long queues formed at South Korea's Incheon airport two days ahead of the start of the Asian Games, an Olympic-size event with 36 sports, 45 countries and about 10,000 athletes.

China, with roughly one-tenth of the competitors, will dominate proceedings, four years after walking off with a record 199 golds and 416 medals overall at Guangzhou 2010.

China's Olympic swim stars Sun Yang, Ye Shiwen and badminton's Lin Dan will hog the limelight along with Japan's emerging athletes and South Korean home favourites.

Attention is also focusing on North Korea's team as they make the rare and politically sensitive trip south to compete for their sports-loving supreme leader, Kim Jong-Un.

Sexual harassment cases tainted the build-up after an Iranian official was kicked out for verbally harassing a volunteer and a Palestinian footballer was accused of groping a woman in the athletes' village.

Organisers are also braced for swathes of empty seats with just 18 percent of tickets sold across the sprawling, 49-venue site as of early this week.

The Games will be declared open at a gala ceremony in Incheon's 62,000-seat, purpose-built main stadium on Friday, headlined by K-Pop stars and "Gangnam Style" singer Psy.

Incheon organisers are calling it a "frugal" Games which at about $2 billion, is costing a fraction of Guangzhou 2010 and pales in comparison with the Beijing and Sochi Olympics.

World and Olympic champions dot the entry sheets, while many teams are using Incheon as a chance to blood young athletes ahead of the 2016 Olympics in Rio de Janeiro.

China's controversial Sun will be the main attraction in the pool and looks set to face South Korea's Park Tae-Hwan and Japan's Kosuke Hagino in the 200m and 400m freestyle.

The two-time Olympic champion is back after a seven-month ban imposed following his brief jail term last year for driving a Porsche without a licence and colliding with a bus.

In athletics, China's Zhang Peimeng will attempt to become the first native Asian to run the 100m in less than 10 seconds.

China will go for clean-sweeps in their specialist sports of diving, table tennis and badminton, where the highly decorated Lin Dan may meet his Malaysian rival Lee Chong Wei.

Japan are trying to make it a men's and women's football double in the home of their arch-foes South Korea, a result which would sorely test the patience of home fans.

And war-ravaged Afghanistan can write another chapter in their cricketing fairytale by winning their biggest title yet, four years after claiming silver in Guangzhou.

Such tales of perseverance, especially from Asia's pockets of severe poverty, will provide a running theme as countries like Nepal and East Timor take on their wealthier neighbours.

And organisers are urging Incheon's residents to come out and support the full range of events rather than just those in which South Korea is strong.

On Monday, an organising committee official said only five percent of athletics tickets had been sold and six percent for football.

"We hope people can come out to watch other nations, too, because this is a festival for all Asians," the official said. "That will really help us stage a successful event."

Despite the slow sales, Incheon officials say the long-term goal is to position what is South Korea's third-biggest city, just west of Seoul, as an Asian financial hub.