Three Iranian men who converted to Christianity to Islam are appealing against criminal convictions for drinking alcohol.
Yasser Mossayebzadeh, Saheb Fadaie and Mohammad Reza Omidi were sentenced to 80 lashes for taking communion wine.
Non-Muslims are allowed to drink alcohol in Iran.
But because conversion to Christianity from Islam is forbidden and regarded as apostasy, the three men are still legally regarded as Muslims.
The third man, Omidi, already has a previous conviction for drinking alcohol. If he is convicted a third time, he is likely to face the death sentence.
World Watch Monitor reports that the three men have also been charged with acting against national security.
Youcef Nadarkhani, the pastor who was in 2009 sentenced to death for apostasy in Iran but subsequently released after he was acquitted in 2012, was also arrested along with his wife Tina and charged with acting against national security. The three converts and Pastor Youcef face up to six years in jail for this offence, if convicted when all four next appear in the Revolutionary Court in Rasht on 15 October.
Since last year, Iranian authorities have already put more than 200 Christians behind bars. At least 43 Christians were arrested in August alone.
Paul Robinson, chief executive of Release International, said: "Why should Christians be lashed for taking communion? And why is Iran refusing to allow its own citizens that most basic of all freedoms, the freedom to choose their own faith? These men have chosen to call themselves Christians. The state should respect that."
Middle East Concern's Rob Duncan said: "The Iranian regime is conducting a very active campaign against house churches at the moment and leaders of house churches are harassed and put under pressure."
Middle East Concern is requesting prayers from Christians worldwide for the Iranian Christian converts.