The numbers of Christians being imprisoned in Eritrea because of their faith is increasing as the government cracks down harder on churches, human rights groups have said.
Catholics are one of three recognised Christian groups
Border tensions in Eritrea are high, making the government nervous about foreign influence - and according to human rights campaigners and Eritrean exiles, this has led to a clampdown on new, mostly Protestant churches.
By law, only three Christian groups are allowed to meet in the country - Orthodox, evangelical Lutheran, and Catholics.
"Things are really stepping up in terms of religious freedom violations," Tina Lambert, from the campaign group Christian Solidarity Worldwide, told BBC World Service's Reporting Religion programme.
"Recently, even the three legal groups have faced repression."
The number of Muslims and Christians in Eritrea is roughly equal, and the Eritrean government fears the new churches may alter that balance - in a way that could create violent conflict.
Eritrean exiles and groups say that there is regular torture and imprisonment of Christians.
In 2003, the US State Department said that some of the detainees "had reportedly been rolled around in oil drums, abused by fellow prisoners, and the women sexually abused."
British evangelist Gerald Godson told Reporting Religion that he spent three days in prison before being expelled from the country after he was arrested for handing out Bibles for the permitted Orthodox Church.
"There was no hostility in their questioning, but there was no explanation for why I was arrested, or what the charges were," he said.
He added that inside jail, he met around 35 Christians in prison - mostly young men and women - all who had not been charged.
"I was so impressed with their peace and their joy," he explained.
"They were definitely encouraging me not to give up."
Ms Lambert said that Mr Godson's account was consistent with that of many Eritreans who have either left or are recent refugees.
She said the churches were perceived as a threat in a country struggling for stability.
"The churches are certainly not doing anything overtly to oppose the government - these are just people wanting to meet," she said.
"The paranoia of the government is really what's at the heart of this - it's always looking for the enemy within.
"Whatever they're doing, they're always going to be suspect because the government wants to control all forms of meeting together."
However, the Eritrean embassy in London denied that there was any religious persecution in the country, stating that "absolute freedom of belief" is permitted.
"Accusations allegedly being made that the government of Eritrea is restricting religious freedom are baseless," it added.
"Facts on the ground show a very different picture to the one presented by organisations or individuals.
"Eritrea is a secular country, with absolute freedom of belief. Peaceful coexistence and religious harmony have been a part of Eritrea's history for centuries.
"The constitution provides for the separation of church and state, and explicitly recognises the freedom and rights of individuals to follow and practice their chosen religion."
The BBC's Alex Last, who spent a number of years in the country, said that the liberation movement which became the government was a secular organisation, and that when it came to power it faced a major challenge in ensuring the balance between Christians and Muslims was maintained.
Groups now claim even permitted churches are being targeted
As a result, it has always tended to "clobber extremists on one side or the other," he said.
However, during the country's border war with Ethiopia, the evangelical Pentecostal church expanded rapidly amongst the young people conscripted into the army and sent to the front lines.
After the war, the idea of groups of young people - particularly those with a military background - meeting together secretly became "anathema" to the government, our correspondent added.
He said he asked the former intelligence chief in Eritrea why they were going after Pentecostal churches, and was told they were a "destabilising influence" and were "proselytising in Muslim areas."
"I asked if they were going to go underground - he said: 'Let them try'," our correspondent added.