According to Barnabas Aid, one of the martyrs is known to be 27-year-old woman Seble Hagos Mebrahtu, who was arrested after being caught reading a Bible in her bedroom. Her death comes as a new wave of raids, which started on New Year's Eve, saw more than 100 evangelical believers detained.

Barnabas Aid says almost an entire congregation - 41 people - from the capital Asmara was taken into custody where they are said to have endured beatings.

"The following day, 27 believers from various underground churches near Asmara were rounded up by the security forces. On January 9, 35 Christians including 15 women and two elderly men in poor health were seized from a house church gathering in the town of Nakfa," the group said in an update.

The World Evangelical Alliance Religious Liberty Commission (WEARLC) said it was no coincidence that this fresh onslaught on Christians in Eritrea began around the time of the Tunisian uprising, which ousted the country's president.

WEARLC Executive Director Godfrey Yogarajah warned that as unrest spreads throughout North Africa and the Middle East, conditions for Eritrean Christians could worsen.

He said, "This may prompt President Isaias to tighten (his) grip on power leading to an even more severe persecution of political dissidents and those from unregistered Protestant Christian groups."

Barnabas Aid says thousands of Christians are believed to be imprisoned without trial in Eritrea's notorious detention system.

A US embassy cable recently published by WikiLeaks confirmed the deplorable conditions suffered by detained Christians and other prisoners.

Barnabas Aid said: "It paints a picture of a cramped 40 by 38 foot cell holding around 600 prisoners, where it was impossible to lie down. They were fed two pieces of bread three times a day; many were so thirsty owing to lack of water that their tongues stuck to the roofs of their mouths. A bucket, which served as a toilet, constantly spilled over with human waste."

The group said there was evidence of torture "from the sound of screaming" and detainees being brought back to the cell by security officials "badly bruised and bleeding".

Barnabas Aid said: "Eritrea's Christians are among the most severely persecuted in the world; they are seen as a threat to national unity because they give their ultimate allegiance to God and not to the state. The government recognises only four religious groups: the Orthodox, Roman Catholic and Lutheran Churches, and Sunni Islam."