Secular liberals say the crackdown amounts to political pandering
Four Algerian Christians have been given suspended jail terms and fines for worshipping illegally.
The case has provoked accusations in the West of religious repression in the largely Muslim country of 33 million - a charge the government denies.
But Christian groups point to the ordered closures of some churches.
The state-appointed Higher Islamic Council said Protestant evangelicals are secretly trying to divide Algerians to colonise the country.
One man, a computer technician, received a six-month suspended jail sentence and a fine of $3,150.
Three others got lighter penalties, two-month suspended jail terms and half the fine.
The four men admitted they had converted to Christianity but rejected the charge against them - that they were holding an illegal religious ceremony when they were arrested.
Some reports also suggest the men were accused of attempting to convert other Algerians to Christianity.
At least two other high-profile trials of Christian converts are on-going.
There are an estimated 10,000 Christians in Algeria.
A 2006 law forbids non-Muslims from trying to convert Muslims and limits religious worship to specific buildings approved by the state - a clause that has been used to close more than a dozen churches in the past six months.
Several mosques have also been closed under the same provision.