The charity Help For Heroes has been swamped with donations, leading to its website crashing after Drummer Lee Rigby was murdered while wearing one of its tops.
The popular military support group was deluged with calls, donations and demands for its merchandise, prompting its website to collapse from the massive internet traffic.
Supporters took to Twitter and social networks in a bid to boost the charity's coffers after the 25-year-old was hacked to death in Woolwich, south-east London, on Wednesday.
Celebrities such as Michael Vaughan, the ex-England cricketer, and the adventurer and broadcaster Ben Fogle were among those urging well-wishers to give money to the charity.
On Thursday, Help For Heroes offered its thanks for the "extraordinary demonstration of support" which had taken it by surprise.
Posting a statement on its holding page, it said: "Since the sad news emerged that a serving soldier had been murdered in Woolwich, Help for Heroes has been overwhelmed with people spontaneously showing their support for the Armed Forces.
"Our website is struggling to cope with this overwhelming reaction from the British public, some of whom are choosing to buy T shirts and hoodies.
"This sudden surge of interest in the work we're doing to help the wounded and their families has taken us completely by surprise.
"We just want to help, and all funds we receive will be used to provide direct, practical support to those affected by their service to our country.
"We ask all our volunteers, fundraisers and donors to remember Lee Rigby's family, colleagues and friends."
The charity said it was "born of a simple desire to help those affected by service to our country."
"It is their duty to serve and our privilege to support them and their families," the charity said.
"We would like to reassure all our volunteers, fundraisers and supporters that all scheduled events will go ahead as planned.
"Thousands of people have visited our website wishing to donate or to buy H4H T-shirts in an extraordinary demonstration of support and defiance of terrorism.
"We are working hard to respond to this level of activity."
It is thought that Help For Heroes will also receive a financial boost from well-wishers expressing their abhorrence at the killing by taking part in fundraising events such as upcoming runs and marathons.