Nine men have been charged with conspiracy to cause explosions in the UK and other terrorism offences.
The suspects - aged between 19 and 28 - are from Cardiff, London and Stoke-on-Trent and were held a week ago during a series of dawn raids by counter-terrorism officers.
They are also accused of engaging in conduct in preparation for acts of terrorism and are due to appear at the City of Westminster Magistrates Court in London.
The men are charged with conspiring to cause an explosion or explosions in the UK "of a nature likely to endanger life or cause serious injury to property" between October 1 and November 20 this year.
They are also accused of engaging in conduct in preparation for acts of terrorism between October 1 and December 20, including by downloading and researching materials and methods; carrying out reconnaissance and agreeing potential targets, and igniting and testing incendiary material.
In all 12 men were held during the dawn raids by unarmed officers on December in Cardiff, London, Stoke-on-Trent and Birmingham. The three other men arrested - two from Cardiff and one from London - have been released without charge, West Midlands Police said.