The Italian government summoned the Afghan ambassador to Rome on Tuesday to express its concern over reports that a man in Afghanistan faces the death penalty because he has converted to Christianity.
Foreign Minister Gianfranco Fini said if the reports proved true, Italy would raise the issue with European Union leaders in an effort to save the man.
An Afghan judge said on Sunday police had detained a man, Abdur Rahman, for converting from Islam to Christianity, adding he could face the death penalty if he refused to become a Muslim again.
"If this news is confirmed, Italy will move at the highest level ... to prevent something which is incompatible with the defence of human rights and fundamental freedoms," a Foreign Ministry statement said.
The statement added that the Italian ambassador in Kabul would contact Afghan authorities to seek an explanation and was also in touch with other EU diplomats in the country.
Former Italian President Francesco Cossiga has written an open letter to Prime Minister Silvio Berlusconi urging him to withdraw Italian troops from Afghanistan if he fails to win assurances from Kabul over Rahman's safety.
"It is not acceptable that our soldiers should put themselves at risk or even sacrifice their life for a fundamentalist, illiberal regime," Cossiga wrote.
Roman Catholic Italy has some 1,775 troops deployed to Afghanistan, a conservative Islamic country where 99 percent of people are Muslim.
Islamic sharia law proposes the death sentence for Muslims who abandon the religion. Afghanistan's new constitution says "no law can be contrary to the sacred religion of Islam".
Emma Bonino, who headed an EU observer mission to Afghanistan for last year's legislative elections, said Italy had done well to ring the alarm bell.
"This episode is extremely worrying, not just because the possible victim is a Christian, but because it indicates the fragility of the Afghan institutions," she told reporters.