In the last two months, Iranian courts have sentenced 18 Christian converts to time in prison for charges including evangelising and creating house churches.

The 18 were sentenced between mid-March and mid-May, according to a report from Persian-language Radio Farda. Thirteen of them were from Shahin Shahr, and were part of a church group that were originally arrested in February 2013. Having been detained and interrogated they were released for about a month before their trial.

They were each given one year in prison, and were banned from leaving Iran for two years.

The other five Christians, who were sentenced at a number of courts around the country, were sentenced to a combined jail time of 10 years and nine months.

According to Fox News they were sentenced according to Article 500 of the Islamic Penal Code, which says that "Anyone who engages in any type of propaganda against the Islamic Republic of Iran or in support of opposition groups and associations shall be sentenced to three months to one year of imprisonment."

When President Hassan Rouhani came to power in 2013, he made assurances that he would improve religious freedom in the country. The news this week that Iran's football team has appointed a Christian as its captain for the first has been seen by some as evidence of such improvements.

But a spokesperson for Elam Ministries told Christian Today that this is "little more than window dressing, when on the ground converts are continuously being arrested and sentenced to prison.

"This is a nation where you cannot print the Bible in Persian, the national language. No matter what other improvements you can point to, in a nation where that's not possible, to what extent can we say that's an improvement?" she said.

Numerous imprisoned Christians have also faced extensions to their sentences, including Farshid Fathi, who lost an appeal at the end of May against an additional year to his already six-year sentence. Fathi converted from Islam to Christianity at the age of 17 and has been imprisoned since 2010.

According to a UN report from March this year, 69 Christian converts were arrested and detained for at least 24 hours in 2014. "Authorities reportedly continued to target the leaders of house churches, generally from Muslim backgrounds. Christian converts also allegedly continue to face restrictions in observing their religious holidays," the report said.

A report from the all-party parliamentary group for interational freedom of religion or belief, also published in March, said: "Christian converts in Iran – and any Christians who minister among individuals from a Muslim background – know they are either already being monitored by the Ministry of Intelligence and Security (MOIS), or that MOIS may identify them and begin monitoring at any time."

Naghmeh Abedini, wife of imprisoned Iranian pastor Saeed Abedini who is also a convert from Islam, told a US Congress committee this week: "I cannot bear to look at my children's longing eyes one more time and explain to them why their daddy is still not home."

Iranian officials have made clear to Abedini that he will not be released unless he abandons what is seen in Islam as apostasy, and re-embraces the religion he was born into.