UFO enthusiasts got a boost today when Welsh police confirmed that one of their helicopter crews had spotted an 'unusual aircraft' flying over Cardiff earlier this month.

An investigation into the sighting had been launched, they said. The police clarification came after The Sun reported a UFO had 'attacked' a police helicopter, following it for several miles over the Bristol Channel.

'The pilot banked sharply to avoid being hit, then launched into a high-speed pursuit. But he was forced to give up the chase as the helicopter's fuel ran low - and the UFO escaped,' the newspaper reported.

The helicopter crew had described the object as 'flying saucer-shaped and circled by flashing lights,' it added.

That description was rather more dramatic than the official police version, which said: 'South Wales Police can confirm its air support unit sighted an unusual aircraft. This was reported to the relevant authorities for their investigation.'

The brief statement avoided the use of the term UFO, or Unidentified Flying Object. At the time of the incident, the helicopter with three men on board was waiting to land at the St Athan RAF base near Cardiff.

The sighting reportedly took place at 12.40am on 8 June. South Wales Police denied there was a pursuit and indicated that the helicopter crew was never in any danger.

A Ministry of Defence spokesman said it had heard nothing about the incident. 'But it is certainly not advisable for police helicopters to go chasing what they think are UFOs,' he added.