Two Oxfordshire men have been arrested in a Europe-wide investigation into child sex offenders.

Detectives in Thames Valley arrested five people in total, including a 57-year-old man from the Wantage area and a 53-year-old man from the Banbury area, officers said today.

Operation Koala was initiated by The Child Exploitation and Online Protection (CEOP) Centre last year and targeted the sexual abuse of children from a modelling website based in Italy.

Customers from all over the world were able to order tailor-made videos depicting abuse, said a police spokesman.

In June the material was passed to CEOP, which has UK responsibility for receiving intelligence and information from overseas on child sexual abuse crimes.

CEOP's Intelligence Faculty analysed the material and passed details of individual suspects to their local police forces, who started their own investigations.

So far, 38 suspects have been arrested in the UK in operations involving 20 police forces, and more arrests are expected in the near future.

Thames Valley Police arrested five people in raids at addresses in Oxfordshire, Newbury, Milton Keynes and Amersham on September 27.

One man was released without charge and four other men have been released on police bail.

The 57-year-old man from the Wantage area was released on police bail until January 4.

The 53-year-old man from the Banbury area has been released on police bail until December 6.

A 39-year-old man from Bletchley and a 56-year-old man from Amersham were bailed until January.

All four men were arrested on suspicion of committing offences relating to the possession, making and distribution of indecent images of children.

Ds Duncan Wynn, from the force's High Tech Crime Unit, said: "These arrests are significant in the fight against child sex offenders and we are dedicated to catching these offenders and stopping the abuse of innocent children."

Jim Gamble, chief executive of CEOP, said: "Yet again we see the technology used by paedophiles to facilitate child abuse now turned against them as a result of coordinated and effective international law enforcement cooperation.

"Operation Koala uncovered the true meaning of 'online child abuse' - in this case, the exchanging of images in which real children were subjected to horrific sexual abuse, often to order."