By Allyn Fisher-Ilan

HOLOT, Israel (Reuters) - A compound of one-storey buildings deep in the southern Israeli desert is now home to some 400 African migrants who face the prospect of being held in custody indefinitely.

The detainees in what the authorities call an "open" detention centre are allowed to leave for a few hours each day, but given its remote location near the Egyptian frontier, travel is impractical.

Israel opened the Holot complex in December after its Supreme Court stopped the practice of jailing illegal migrants for up to three years in regular prisons.

But in what the migrants call a cruel twist and rights groups say is a rights violation, a law passed the same month allows the migrants to be detained indefinitely, pending the resolution of their requests to stay in Israel.

"I went to renew my visa, and suddenly I wound up here. This is terrible," said Eritrean Hagos Fdwi, 30, who worked in a restaurant in Tel Aviv.

More than 50,000 Africans - mainly Sudanese and Eritreans - have crossed into Israel surreptitiously through a once-porous, and now fenced, Egyptian border in the past eight years.

Many say they seek asylum from war-torn homelands, but Israel dismisses most as illegal job seekers although some have been granted limited visas.

Authorities complain of heightened social tensions in more impoverished parts of Tel Aviv where Africans settle. Prime Minister Benjamin Netanyahu has said the influx threatens Israel's Jewish character and wants the majority of migrants removed.

But rather than conduct outright deportations, Israel is trying to coax migrants to return home voluntarily - including offering a cash incentive - or persuade third countries to accept them.

So far, relatively few have taken the money, though Israeli officials say 2,000 left in 2013, up from a reported 400 or so in 2012. No third-country safe havens have been established.

Daniel Solomon, an Interior Ministry legal adviser, said Holot was established to get migrants off the streets and out of the job market.

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"Legally people can be held at the open facility indefinitely, but the idea is for it to be a transit (point) for migrants before they go back home or to a third country," he told reporters in January.

Journalists have not been permitted to enter the compound, but Reuters was able to interview a dozen or so detainees who ventured outside its gates.

Some said they were bused from Tel Aviv or surrounding areas after visiting the visa office, arriving at the centre with just the clothing on their backs.

Many said they do not take the opportunity to leave the facility each day. The closest town, Beersheba, is about an hour's drive away, and detainees are required to check in every few hours. Failure to do so could mean transfer to a conventional prison.

There were few complaints about accommodations, said to include television and three meals a day, with 10 men sleeping in an amply sized room. No women or children are being held.

FRUSTRATION

Holot has a capacity to hold more than 3,000 inmates and human rights groups say at least 2,000 more migrants have received summonses to report there by next month.

The rights groups argue that many of the migrants are worthy of political asylum, citing unrest and oppression in their homelands, and have petitioned the Supreme Court against the law.

The UN High Commissioner for Refugees representative in Israel, Walpurga Englbrecht, said unlimited incarceration at Holot did not "comply with international human rights norms."

"What is more disturbing is there are no release grounds from Holot, the only way to get out is signing up for voluntary departure," Englbrecht told Reuters.

Anger over the facility has triggered a series of protests by migrants in the past month, including a march to Israel's parliament and crowded vigils in Tel Aviv.

When a Reuters TV crew showed up outside the facility recently, some of the detainees held up signs calling for asylum. Three detainees walking down the road crossed their wrists over their heads as if they were handcuffed.

Detainees spoke to Reuters mainly of boredom and frustration at seeing no quick way out of their predicament. Two said they had been separated from their wives and children, although Israel said it avoids sending men with families to the facility.

Solomon Hagos, 25, said he has been in detention in Israel since he entered illegally 18 months ago. He said he fled an Eritrean military prison in 2012 and was gang-raped over several days by three men who held him captive in Egypt's Sinai desert before he crossed into Israel.

"My life is nothing but a prison," said Hagos, whose asylum petition was rejected last month.

Robel Yohanns, 23, of Eritrea, was more hopeful than most of the detainees, however.

"I'm just going to sit patiently and wait for them to change the law, again," he said.