The new commissioner of the Metropolitan Police has promised to "bear down" on large rises in violent crime in London.
Gun offences surged by 42% in the capital between April 2016 and April 2017, and knife crime went up by 24%.
Cressida Dick said the figures "worry" her, and that tackling the two crimes will be a priority.
She also warned there would have to be "some changes" to security following the Westminster terror attack.
The annual statistics released by the Met last week showed there were 2,544 gun crimes in the city, compared to 1,793 the previous year.
There were 12,074 recorded knife offences between April 2016 and April 2017, up from 9,742.
Ms Dick, who has worked for both the Met and the Foreign Office, told BBC Radio 4's Today programme that she was unsure whether the numbers proved a "trend" due to changes in how the force records crime.
"But if it is the case that gun crime and knife crime is going up then that is of huge concern to me," she added.
"It will mark my commissionership, trying to bear down on violence in general and those two crimes in particular."
On Ms Dick's first day in the job, she spoke at the funeral of PC Keith Palmer, who was stabbed by Khalid Masood during last month's attack in Westminster and was one of five people killed.
She said it was "very hard to say" whether there would have been a different outcome for the 48-year-old father of one if he had been armed, but said lessons would be learned.
'More physical protections'
"There will have to be some changes," said Ms Dick, "but the man who carried out the terrible, terrible attack... he wanted, we assume, to change the way this country is.
"It was an attack on our values and our democracy, quite clearly, and people in the country value the fact they have freedom... and that the police are largely unarmed. That is something I want to protect in the future.
"But I am sure we will see more physical protections for crowded spaces."