British Cops Bust 4 on Terror Suspicion Before Royals' Busy Weekend

Police detained the men in West London.

The arrests came two days before Remembrance Sunday, when a service is held at the Cenotaph memorial in central London attended by most of the royal family -- though specific targets of the alleged plot were not made public.

The queen and the royal family also are set to attend an event at the historic Royal Albert Hall in London tonight, part of a weekend full of public events the royals attend to remember the nation’s war dead.

Neither police nor the palace was directly linking the arrests to Remembrance Day weekend events.

However, the arrests were made during the day on Friday, not overnight as is usually the case, which suggested the operation was done in a hurry.

ABC News' Michael S. James contributed to this report.