* Recall two-day ordeal at isolated natural gas plant
* Witnessed killings, hid in fear from Islamist militants
* Fate of many hostages remains unknown
By Lamine Chikhi
ALGIERS, Jan 18 (Reuters) - A Frenchman spent a day and two nights in terror, boarded up under his bed, certain he would be found and killed. An Algerian radio operator saw his French supervisor's corpse. A Northern Irish engineer saw four truckloads of other hostages blasted to pieces in an Algerian military strike.
The siege of a natural gas plant deep in the remote Sahara desert of Algeria is not yet over, but the stories of survivors so far contain tales of shattering trauma that experts say may never heal.
Hundreds of Algerians and scores of foreigners were trapped inside the gas complex captured by gunmen before dawn on Wednesday.
Although official accounts are contradictory and the fates of many are still unknown, Algerian officials say as many as 30 Algerian and foreign hostages may have been killed and potentially dozens of foreigners remain unaccounted for.
The attackers who arrived on Wednesday before dawn ran through the vast compound, which includes a huge residential barracks and a gas processing plant, searching for foreigners, said Abdelkader, 53, a worker from the nearby town of In Amenas.
"The terrorists told us at the very start that they would not hurt Muslims but were only interested in the Christians and infidels," he recalled. "'We will kill them,' they said."
His voice choking with emotion - "I'm a lucky man," he said over the sound of children playing and a television relaying the latest news - Abdelkader described how he managed to escape along with many of the hundreds of Algerians initially detained.
"I am still choked, and stressed," he said, adding that he feared many of his foreign colleagues may have died. "The terrorists seemed to know the base very well. Moving around, showing that they knew where they were going."
Algerian radio operator Azedine, 27, said he saw the body of his French supervisor. One of the militants had taken the dead Frenchman's ID badge and was putting it on.
"My supervisor was a great man; I learned a lot from him. He had been shot, but I did not see the execution. All I saw was his body when I ran with some colleagues to leave the base," he told Reuters, clearly still in shock.
The kidnappers eventually announced they were holding 41 foreigners. Among the other foreign workers still hiding in the compound was French catering manager Alexandre Berceaux.
"I heard a huge amount of shooting. There was an alarm telling us to stay where we were but I didn't know if it was real or a drill," he later told Europe 1 radio.
He survived by staying in his room away from other foreigners, hidden behind a barricade of wooden planks. Algerian colleagues sneaked him food and water.
"I was completely isolated ... I was afraid. I could see myself already ending up in a wooden box," he said from the military base where he and other freed hostages were taken by the Algerian army.
The foreigners captured by the gunmen were bound, and some were made to wear explosive belts, while outside the Algerian army surrounded the compound, declaring it would not negotiate.
The captors told Mauritanian media they would kill the hostages if the army tried to storm the building. Algerian officials said the captors demanded safe passage out of the compound with their prisoners, but the government refused. The captors said the army tried to storm the building overnight.
In the second morning, the hostages were allowed to phone out to media, in what appeared to be an attempt by their captors to persuade the military to back off.
Still a prisoner inside the building, Northern Irish engineer Stephen McFaul spoke to Al Jazeera television.
"The situation is deteriorating. We have contacted the embassies and we call on the Algerian army to withdraw ... We are worried because of the continuation of the firing," he said.
Soon after, he and other hostages were herded into five trucks by captors who wanted to move them. According to his brother, Algerian forces fired on the convoy. McFaul survived, but saw four of the vehicles destroyed.
"The army bombed four out of the five of the trucks, and four of them were destroyed," Brian McFaul said. "The truck my brother was in crashed and at that stage Stephen was able to make a break for his freedom. He presumed everyone else in the other trucks was killed."