A long-standing anarchist bookshop has been badly damaged in a suspected firebomb attack.

Police investigating the blaze at the Freedom Press bookshop in Whitechapel High Street, east London, are treating it as suspicious. Firefighters were called to the premises at around 5am on Friday and spent two hours extinguishing the blaze. No one was injured.

Around 15% of the ground floor suffered fire damage but the flats above the shop were unaffected.

Freedom Press, which owns the bookshop and publishes a monthly anarchist newspaper, is asking for donations to repair the damage as the premises was uninsured. "We're all absolutely shell-shocked," said Jayne, a member of Freedom Press who did not want to give her surname. "What's particularly annoying is that we couldn't afford to renew our insurance and it ran out last week.

"There's a lot of fire and water damage, which doesn't go too well with books. This wasn't an accident. Somebody had to lift up a metal shutter to break the window to start the fire. We do get this kind of trouble sometimes."

A post was uploaded on the Freedom Press Twitter page which said it was not yet clear whether its newspaper archives had been damaged in the blaze.

"Not sure yet whether archives survived – we had one of only a few sets covering almost the entire printed history of the paper boxed in shop," it read.

Further tweets stated a clean-up had been arranged to take place at the shop from 1pm on Saturday and a donations page was being set up.

Freedom Press was founded in 1886 by a group of friends, including Charlotte Wilson and Peter Kropotkin, and describes itself as the "largest anarchist publishing house" in the country.

It claims to stock thousands of books, newspapers, pamphlets along with magazines, periodicals and newsletters from major anarchist and radical groups.

A Metropolitan police spokesman said: "Inquiries into the circumstances of the fire are under way but at this early stage it is being treated as suspicious."

No arrests have been made.