TOKYO -- Ctrip, the largest online travel agency in China, faced questioning Tuesday by Japan's tourism agency and industry groups after its Japan website allegedly let customers book rooms that turned out to be taken, in a major hiccup going into the year-end travel season.

Ctrip's Trip.com site for Japanese customers apparently had at least 37 cases, involving 10 partner businesses, in which travelers were shown vacancies at hotels or traditional ryokan inns that were already fully booked. Customers who tried to reserve such rooms were even sent confirmation that their booking was complete.

The travel giant is also suspected of selling fraudulent packages that included bookings at higher-than-normal prices.

Ctrip has suspended dealings with the partners in question. It denied any involvement in dishonest behavior, saying the problem stemmed instead from "insufficient oversight of businesses" listed on its site.

One person affiliated with a ryokan, however, said the issue "will be mistakenly perceived as an error on our end" when the problem lay with Ctrip.

Ctrip contracts with more than 500 businesses internationally to offer bookings using up-to-date information on vacancies at partner hotels, according to the All Japan Ryokan Hotel Association.

The problematic bookings apparently involved customers paying up front to reserve an open room, as opposed to Japan's usual practice of booking in advance but paying on arrival. Ctrip says advance payments are common overseas, but has stopped the practice in Japan.