Image caption Many of the children were contacted through the internet, police said

Police have arrested 190 people in a major US crackdown on images showing child sex abuse, officials say.

The month-long "Operation Orion" also resulted in 18 children being rescued, federal agents said.

Arrests were made mostly in the US but also took place in countries including Spain, Argentina, the UK and the Philippines.

The official in charge said many of the cases began with a child chatting with someone they had encountered online.

"Let this operation be a warning to anyone who would think they can use the internet to exploit children - we are out there looking for you, we will find you, and you will be prosecuted," Immigration and Customs Enforcement (ICE) Director John Morton said in a statement.

The statement said that Operation Orion focused on the production, possession and distribution of child pornography in videos and photographs.

Those arrested included a 35-year-old babysitter in Louisiana suspected of using a seven-year-old child to make pornography.

A 28-year-old man in Michigan was found to have more than 1,200 images and 109 videos of child sex abuse on computers and media storage devices, officials said.

Eight men were also arrested in Los Angeles, including one who met his alleged 12-year-old victim on the internet.

He was charged with enticing a minor to commit lewd acts after agents pretended to be the girl online and arranged to meet him at a shopping centre.

The ICE statement said that they had also "identified and rescued" 18 victims of child pornography.

No details were given of the arrests conducted abroad. The US Justice Department also listed Sweden, Serbia and the Netherlands as involved in the operation.

US Assistant Attorney General Lanny Breuer said in a statement: "This operation uncovered a dangerous and depraved group of criminals who were devoted to trading sexually explicit images of children under the age of five."