A detained Iranian employee of the British embassy in Iran has been charged with acting against Iran's national security, his lawyer has said, according to Al Jazeera.

Abdolsamad Khorramshi, who is representing Hossein Rassam, said on Saturday that his client was being held in Evin prison in Tehran, the capital.

"The accusation is that he has been acting against national security," Khorramshi said.

"But what he has done, or how he has done it, is something that will be determined later on, if there are reasons or proof."

Anoushka Marashlian, an independent Middle East analyst, told Al Jazeera that the exact charges against Rassam are unclear.

"He's been seen as acting against the national interest, but they haven't clarified as to what he has been charged with," she said.

"I think [the British government] needs to wait to see what the actual charges are. Is he being charged with treason, which is the accusation that some have levelled against supporters of Mousavi?"