LONDON, Dec. 7 (Xinhua) -- The number of suspects arrested in terrorism investigation in the United Kingdom has reached a record high, new figures from the British Home Office revealed here Thursday.
A total of 400 people were held over terror-related offences in Britain in the year to the end of September, up 54 percent on the previous 12 months.
The Home Office said the increase in the year to September was due partly to the 64 arrests made after the attacks in London and Manchester, bringing the total to the highest number since records began in 2001.
The latest figures showed 12 people were arrested for the Westminster Bridge attack, 23 for Manchester Arena, 21 for London Bridge, one for Finsbury Park mosque and seven in connection with Parsons Green.
This was the highest tally since data collection started in 2001. Of those held, 58 were female, also the highest number on record.
The figures reflect the growing threat from Islamist terrorism 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."
Meanwhile, the figures also revealed that there were year-on-year increases in arrests for terrorism-related offences across all age groups and ethnic groups, including a 77 percent rise in white suspects held, from 81 to 143.
They showed an annual jump of more than a third in arrests linked to international terrorism, from 212 to 292, such as the Islamic State, also known as ISIS or Da'esh.
The figures came just two days after Parker said that nine terror plots had been foiled in the UK in the past year.
The figures were announced just a day after two men appeared in court in London Wednesday on charges related to an alleged plot to blow up 10 Downing Street and kill British Prime Minister Theresa May.
Both men were detained on Nov. 28 during raids by armed officers from the British police's Counter Terrorism Command. They had been held for questioning since their arrests and were charged with the terrorism offences Tuesday evening.
Briefing the British cabinet Tuesday on the foiled assassination plot, Parker said the Islamic State had been defeated in Syria and Iraq but was continuing to orchestrate attacks on the United Kingdom.
Militants are increasingly using social media to try communicate with would-be attackers, he said.
Also on Tuesday, the prime minister's spokesman said, "Cabinet ministers heard that while Da'esh suffered major defeats in Iraq and Syria, this did not mean the threat is over. Rather it is spreading to new areas, including trying to encourage attacks in the UK and elsewhere via propaganda on social media."