TEHERAN, Iran - US Secretary of State Hillary Clinton said on Sunday she was "deeply disappointed" over the eight-year prison sentence given to two US citizens who have said they had strayed unwittingly into Iran.

"We are deeply disappointed that Iranian judicial authorities have sentenced Shane Bauer and Joshua Fattal to eight years in prison," Clinton said.

"We continue to call and work for their immediate release - it is time for them to return home and be reunited with their families."

The lawyer for the two US citizens, convicted of spying in Iran, said he would appeal their eight-year sentence.

Bauer and Fattal were arrested on the border with Iraq in 2009 where they said they were hiking. They were found guilty of illegal entry and espionage, a verdict likely to further strain Iran's already poor relations with Washington.

"We have 20 days to appeal and I will try my best to use all legal means to annul the sentence," lawyer Masoud Shafiee said.

Bauer, 28, and Fattal, 29, share a cell in Teheran's Evin prison. They had pleaded not guilty to the charges at their closed-door trial which ended on July 31.

"Josh and Shane were informed about the verdict yesterday (on Saturday)," Shafiee said, adding that he had not seen them in person. The two years they had already served would count toward their 8-year sentences, he said.

They were arrested on July 31, 2009 near Iran's border with Iraq, along with Bauer's girlfriend, Sarah Shourd, 32, who was released on $500,000 bail in September and returned home to California where she has been campaigning for their freedom. Confirming a leaked report of the sentence, Teheran Prosecutor-General Abbas Jafari Dolatabadi told a news conference that no verdict had yet been passed on Shourd who did not return to Iran to stand trial.

The "hikers" affair has heightened tensions between Teheran and Washington, which cut diplomatic ties after the storming of the US embassy in the wake of the 1979 Islamic Revolution. Their trial took place behind closed doors and the evidence against them has not been made public.

Reuters