(CNN) -- Six men have pleaded guilty to planning a terror attack against a right-wing group's rally in the United Kingdom last year -- a plan police say failed because the would-be attackers arrived after the event ended -- authorities said Tuesday.
The men, all from the West Midlands in England and in their 20s, planned to attack an English Defence League rally in Dewsbury with guns, knives and an explosive made from fireworks packed with nails and ball bearings, West Midlands police said.
The six -- Omar Khan, Zohaib Ahmed, Mohammed Hasseen, Mohammed Saud, Anzal Hussain and Jewel Uddin -- pleaded guilty this month to preparing for terrorism.
Police said five of the men traveled with the weapons to a rally of the EDL -- known for criticizing Islamic extremism -- in late June. But by the time they arrived, the rally had dispersed, police said.
A police officer later stopped one of their two vehicles, concerned that it was in poor condition, and seized it because it appeared to have no insurance. A subsequent search of the vehicle revealed two shotguns, kitchen knives, machetes and an explosive device with shrapnel, police said.
Also in the vehicle was a note addressed to the "enemies of Islam," Queen Elizabeth II and Prime Minister David Cameron, police said.
"To the EDL (English Drunkards League), O enemies of Allah! We have heard and seen you openly insulting the final Messenger of Allah ... you should know that for every action there is a reaction. Today is a day of retaliation (especially) for your blasphemy of Allah and his Messenger Muhammad," the note said, according to police.
CDs of speeches from the late militant cleric Anwar al-Awlaki also were found in the vehicle, police said. Al-Awlaki was killed in a U.S. drone strike in a remote part of Yemen in September 2011.
Hasseen, who police said did not travel to the rally, also pleaded guilty to an additional charge of possessing documents likely to be of use to a person preparing for or committing terrorism.
Sentencing for the six is scheduled for June.