He is thought to have a bite mark on one shoulder after one of the victims bit him during a struggle.

The man struck as the two women, aged 21 and 23, were returning to the Sze Lok Yuen youth hostel, off Tai Mo Shan Road, on Sunday night. The pair, who arrived in Hong Kong last week, had checked into the hostel on Sunday afternoon.

Police said the victims' ordeal began about 9pm on Sunday after they got off a bus on Route Twisk near the junction of Tai Mo Shan Road and then walked up the hill, returning to the hostel.

The English-speaking man, believed to be either South Asian or South American, got out of a black van and followed the women. There were another two men in the van, which followed for a while before driving off.

Police said the man, wearing an orange shirt and carrying a can of beer, followed and teased the women during their 45-minute walk to the hostel. The victims told police he appeared to have been drunk.

As they reached an unlit path off Tai Mo Shan Road, about 100 metres away from the main gate of the hostel, the man began to indecently assault the two women.

'The culprit first molested the two victims and both women resisted,' Assistant Tsuen Wan District Commander (Crime), Superintendent Chan Kwok-keung said.

'One of them drew out a folding knife from her rucksack and threatened him to stop indecently assaulting them. But he disarmed her.

'The man grabbed and threw them to the ground and then he pinned them on the ground, threatened them with the knife and forcibly raped them.'

Police said both victims shouted for help but no one could hear them. Two staff members were in the hostel but there were no other guests.

Assistant Tsuen Wan District Commander (Crime), Superintendent Gareth Williams, said: 'He is a powerful man. He's about five feet and 10 inches [1.77 metres] tall and strong in build. Unfortunately, he was able to physically overpower both of them.'

The victims ran back to the hostel to seek help after the man fled on foot with the knife. A report was made to the police about 9.30pm. Officers searched the area but no one was arrested.

The women suffered minor injuries to their arms and legs and were taken to hospital for treatment.

Mr Williams said police were very concerned about the incident and appealed to anyone with information to contact them.

Mr Chan said the area had been very quiet, with no serious crime reported there in the past two years.

Estella Chung Kim-wan, acting general manager of the Hong Kong Youth Hostels Association, which runs the hostel, said: 'We're shocked by the incident. They [the two victims] came to Hong Kong for fun but this happened to them.'

The association's administration manager, Kelvin Chu Ka-him, said it would ask police to step up patrols in the area and would improve lighting near the hostel.

Representatives from the travel industry expressed concern about the attack but they believed it was an isolated case and would not affect Hong Kong's tourism industry or image overseas.

- The Sze Lok Yuen hostel, left, is a former experimental farm. The hostel has 88 beds and charges $50 a night. It is one of seven run by the Hong Kong Youth Hostels Association

- A full-time supervisor manages the self-catering hostel, which is closed if no one is staying there

- Few foreign tourists use it because the nearest bus stop is a 45-minute walk away on Route Twisk

- There have been burglaries at the hostel, but no serious crime