Environmental campaigner Greta Thunberg has told Swedish officials she is being subjected to harsh treatment in Israeli custody after her detention and removal from a flotilla carrying aid to Gaza, according to correspondence seen by the Guardian.

According to the correspondence, Israeli forces are also reported by another detainee to have taken photographs where Thunberg was allegedly forced to hold flags. The identity of the flags are unknown.

In an email sent by the Swedish foreign ministry to people close to Thunberg, and seen by the Guardian, an official who has visited the activist in prison said she claimed she was detained in a cell infested with bedbugs, with too little food and water.