Police are investigating a Bristol-based internet travel firm that has allegedly taken money but failed to book flights.

Passengers who have booked flights to Pakistan through www.cheapflightsuk.info say they have arrived at airports to find they are not booked on flights. Six people have complained to police in 24 hours.

Some spent thousands of pounds on travel arrangements and arrived at Heathrow Airport to find no bookings had been made. One couple paid for return flights but are now stranded in Islamabad because only a single flight had been booked by the company.

Police are looking into the firm, which has offices in Fishponds Road and Baldwin Street in Bristol. Officers say they have not been able to find anyone from the company at those addresses.

Police say inquiries have revealed that the company is not ATOL-accredited. They say many of the payments were through bank transfers rather than credit cards, which means there is unlikely to be any security or protection.

The customers include a 27-year-old security officer from Cricklewood, London. He was due to fly with five members of his family to Dubai and then Islamabad where he is to get married in November.

The man, who asked not to be named, said: "My father saw an ad on TV for cheapflightsuk.info. He rang the travel agent and was quoted £500 per ticket.

"He didn't book immediately but shopped around a bit and then rang a few days later. The woman said if he didn't book then the price would go up the next day."

The Londoner paid £2,700 in total which was transferred from his NatWest branch to a Barclays account. The family received print-outs of electronic tickets complete with reservation codes but one of the names of the passengers was wrongly spelled.

There was no response when the family emailed the company and on Tuesday when they telephoned, the line was dead. When they emailed, pretending to ask about more tickets, there was an immediate response.

Police have been liaising with trading standards officers in Bristol. Anyone who thinks they have a booking to Pakistan through this firm is advised to contact directly the airline they believe they are booked on to verify if their seats are booked and paid for.

Detective Constable Greg Brunt said: "The company appears to have been advertising on various television channels, and we think they've been targeting Indian and Asian travellers during Ramadan. We don't know at this stage whether this is a case of a company going out of business, or whether there has been any potential fraud or deliberate deception."

The company's website has no telephone number, customers are invited to book online.