The admission came after the Thai Airways International labour union complained of construction workers and security guards sexually harassing female employees on night shift.

"Security is not extensive enough, partly because the airport is so huge with so many users," Somchai said.

He had ordered an increase in security guards, screening of construction workers as well as other tough measures.

Officials would be asked to consider a union request that construction workers leave the airport by 5pm.

As well as airline staff, women employees at duty-free shops had complained about harassment and peeping toms.

Airports of Thailand (AOT) president Chotisak Asapaviriya yesterday said Suvarnabhumi had about 1,000 security guards. It would boost the number by 300 on additional night patrols.

"We will also increase lighting," he said.

Chotisak asked all victims of harassment to come forward so disciplinary measures could be taken.

"We can check security cameras. If there is concrete evidence, we will immediately dismiss offenders," he said.

The airline union revealed the incidents on Tuesday. It said most harassment occurred in employee-only zones and parking areas.

Suvarnabhumi commenced commercial operations in late-September but many areas remain under construction or renovation.

Acting union chairman Somsak Srinual said yesterday harassment started as verbal only but had become increasingly serious. Some men had attempted to touch women. Other employees reported peeping toms in toilets.

Somsak was also investigating rumours of rapes, although no complainants had come forward.

He advised staff to use internal airport emergency telephones if they were attacked or witnessed an attack. "Come forward and we can check security cameras," he said.

The director vowed there would be no tolerance of sexual harassment - verbal or worse. "Offenders will be immediately reprimanded if witnessed and repeat offenders will be brought to police attention," he said.

Security officials would screen all contract workers entering and leaving the airport. "We have asked police to help ensure safety inside the airport too," he said.

Deputy National Police Commissioner General Ajiravid Subarnbhesaj said officers would ensure safety at the airport.

In a related development, an informed source revealed Transport Minister Admiral Theera Haocharoen was unhappy with AOT president Chotisak.

Since Suvarnabhumi opened, it has been plagued by problems - including baggage handling, check-in systems, a lack of toilets, a leaking roof, noise pollution and security problems.