LONDON - Terror arrests have risen to a record high in the wake of the attacks in London and Manchester with more than 400 suspects held by British police in the past year, official figures revealed Thursday.

The British Home Office statistics showed that 412 terrorism-related arrests were made during 2017, an increase of 58 percent over the 261 people detained in the previous year.

The record figures included 12 people arrested for the Westminster attacks in March, the 23 people linked to the attack in Manchester in May, 21 arrests connected with the London Bridge attack in June and one person arrested in connection with the Finsbury Park mosque attack later that month.

A further seven arrests were made in connection with the attack on Parsons Green tube station in September.

The vast majority of those held in 2017 were linked to either international or domestic terrorism.

There were 300 arrests in the international category, which covers suspected activity linked to or motivated by terrorist groups based outside the UK, such as Islamic State.

In the domestic category, which relates to cases where there is no connection to either Northern Ireland-related or international terrorism, there were 71 arrests.

The figures reflected the growing threat from Jihadists in Britain. The director general of MI5, Andrew Parker, spoke in October of "a dramatic upshift in the threat this year" to the "highest tempo I've seen in my 34-year career."

The detailed Home Office figures showed that of the arrests, 135 people were charged, 110 of them for terrorism-related offences. Of these, 29 had been prosecuted and convicted by the time the latest data was compiled.

More than half -- 228 or 55 percent -- were released without charge while a further 33 were released on bail pending further investigation, and 13 faced alternative action.

So far 29 of the 110 people charged with a terrorist offence in 2017 have been prosecuted. All of them were convicted. A further 76 are awaiting prosecution. The remaining five cases have either not proceeded or are pending.

The latest figures showed that by the end of 2017 there were 224 terrorist prisoners in jails in Britain, an increase of 24 percent, or 43, over the previous year, and continuing the upward trend seen in recent years.

The overwhelming majority, 86 percent, held Islamic extremist views while 9 percent were rightwing extremists including from the recently banned National Action, and the remaining 5 precept classified as "other ideologies."

Of the arrests, 48 percent were of suspects aged 30 or over. There were 27 arrests of under-18s which was the highest number of juveniles held in a year since records began.

White people accounted for 145 arrests, the highest tally so far, and a third of suspects arrested were foreign, but 68 percent were Britain citizens.

The quarterly terrorism powers statistics also showed that the Metropolitan police have stepped up the use of their counter-terror stop and search powers. The number of searches carried out rose 59 percent in 2017 to 767 from 483 the year before.

However, the number of people stopped and examined at ports and airports under counter-terror powers continued to fall in 2017. There were 16,349 examinations last year, a fall of 16 percent compared with the previous year, reflecting the recent downward trend.

The number of people detained under these port powers, however, rose 10 percent in 2017 from 1,539 to 1,700.