The launch of a giant ferris wheel in Malaysia's tourist town of Malacca went sour when a power cut trapped dozens of people on the inaugural ride, reports said today.

Some 50 passengers including tearful children and an eight-month-pregnant woman were stuck 25 metres above the ground in the pitch dark last night until rescuers managed to bring the gondolas down manually half an hour later.

The New Straits Times said the incident happened just as Malacca's state governor and chief minister arrived for their turn on the new 3.3 million ringgit ($A988,00) tourist attraction built on the banks of the Malacca River.

"I was shaken. This is a sign of poor safety features. I feel the ferris wheel is not ready for operations yet," Ibrahim Mohamed, whose daughter and grandchildren were trapped on the ride, told the daily.

AFP