All the men arrested last week are from Birmingham, Britain's second biggest city, police have said (file photo).

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Six men from Birmingham, England, arrested last week, are charged Sunday

The two traveled to Pakistan for terror training, according to police

Those two, and one other, were "planning a bombing campaign"

CNN  — 

Six men were charged Sunday night in England for terrorism-related offenses, just less than a week after being arrested as part of what authorities called a “major operation.”

All of those arrested September 19 are from Birmingham, Britain’s second largest city, the West Midlands Police said in a news release.

So, too, is a 20-year-old man who was arrested Thursday and “continues to be questioned.” Authorities have until September 29 to press charges, release the man or apply for a warrant so he can detained longer without being formally charged.

Authorities said they men were not armed when they launched last week’s operation based on amassed intelligence, police said.

On Monday, Assistant Chief Constable Marcus Beale described the arrests as necessary “in order to ensure public safety.” He declined then to go into details about what the men were suspected of, saying “the operation is in its early stages.”

Britain did not change its terror threat level in light of the arrests, leaving it at “substantial.”

The six men will appear at West London Magistrates Court Monday afternoon.

Irfan Nasser, 30; Irfan Khalid, 26; Ashik Ali, 26; and Rahin Ahmed, 25, will be charged with engaging in conduct in preparation of terrorist acts, West Midlands police said.

Police allege that Nasser traveled to Pakistan for training in terrorism, “making a martyrdom film,” “planning a bombing campaign,” “planning a suicide bombing campaign/event,” “collecting money for terrorism,” “advising and counseling the commission of terrorist acts by providing information about training in Pakistan,” “counseling on explosives and detonators” and “stating an intention to be a suicide bomber,” according to the news release.

The others face similar, if generally fewer, accusations according to the release for West Midlands police. Khalid also is said to have traveled to Pakistan for terror training.

Bahader Ali, 28, is facing two charges – having information about acts of terrorism and entering into a funding arrangement for the purposes of terrorism. Mohammed Rizwan, 32, was charged with having information about acts of terrorism, police said.

Ashik Ali and Bahader Ali are brothers, police noted.