RAMALLAH, West Bank, Feb 1 (Reuters) - Mahdi Abu Ghazali says he went to prison voluntarily out of fear for his life.

No ordinary inmate, he is reachable on his cell phone.

Abu Ghazali turned himself in to Palestinian security forces in the West Bank on Jan. 7, together with eight other Palestinians who were told they risked sharing the fate of three men shot dead by the Israeli army two weeks earlier.

We were advised by the security forces that we should go to prison to preserve our lives, Abu Ghazali told Reuters by phone from Jnaid prison, run by the Palestinian Authority near Nablus.

A former member of the al-Aqsa Martyrs' Brigade, Abu Ghazali thought he was safe from pursuit by Israel, which has occupied the West Bank since 1967.

He had been included in an Israeli amnesty that had covered scores of members of the Fatah-affiliated militant group, he said. Yet so was one of the three men killed by the Israeli army in Nablus on Dec. 26.

The army suspected the three former al-Aqsa Martyrs' Brigade men of killing a Jewish settler two days earlier. The Palestinians who detained Abu Ghazali told him of Israeli allegations that he was planning to avenge the Nablus killings -- a charge he flatly denied.

It was 10:30 p.m. They said we had until midnight to get to Jnaid prison or the other side (Israel) would act in its own way, Abu Ghazali said.

The security forces' swift action to ensure no further bloodshed reflects Palestinian President Mahmoud Abbas's determination to avoid paralysis in the peace process with Israel spiralling into violence in the West Bank.

Yet such detentions pose a public image problem for the security forces. They strongly reject accusations of collaboration with Israel from critics including the Hamas Islamist group that governs Gaza.

We do not imprison anyone according to what Israel wants, said Adnan Dameri, spokesman for the Palestinian security forces which exercise control over islands of West Bank territory under interim peace agreements with Israel.

SAFER INSIDE

The men in Jnaid prison had been detained out of genuine concern for their lives, he added, describing the three killings in Nablus as Israeli executions aimed at undermining public confidence in the Palestinian security forces.

The Israeli army has said the three had ignored orders to surrender. One of them was found holding a gun. None of them had opened fire. The soldiers had assumed each was armed and dangerous, the army said.

An investigation by B'Tselem, an Israeli human rights organisation, has raised a grave suspicion that the soldiers acted unlawfully. In at least two of the cases, the soldiers had made no attempt to arrest the men, it said.

Abu Ghazali, who fought in the armed Palestinian uprising, or Intifada, earlier this decade, said he believed Israel was hoping to provoke a violent response. It would not come from him, he added.

Aged 36 and married five months ago, he says he had been trying to build a normal life in Nablus, where he had been working at his brother's shoe shop until his recent detention.

He spent several years in an Israeli jail during the Intifada. It's no surprise he is treated well by his current jailers: the Palestinian security forces in the West Bank are dominated by Fatah.

Although he is now in a Palestinian jail, Abu Ghazali has no doubt that his release date depends on Israel. The security forces are convinced that Israeli allegations are groundless, he said.