GENEVA (Reuters) - The United Nations human rights office called on Malta on Tuesday to drop terrorism charges against three African teenage migrants arrested for hijacking a small commercial tanker that rescued their vessel off the coast of Libya.

Slideshow ( 2 images )

The three, who have pleaded not guilty, were among 108 Africans rescued by the El Hiblu 1 tanker in late March. They are accused of threatening the crew to try to force the boat to go to Malta and not take them back to Libya.

Many of the migrants, including several children, had been dehydrated and exhibiting “clear signs of torture”, U.N. human rights spokeswoman Ravina Shamdasani said.

The three youths - one from Ivory Coast and two from Guinea - are due to appear in court on May 20, she said.

“The accused, aged 15, 16 and 19, have been charged under Maltese laws for allegedly hijacking the ship and forcing it to go to Malta. Some of the charges are punishable by life imprisonment,” Shamdasani told a news briefing.

While the circumstances around the captain’s decision to finally steer the ship to Malta are disputed, the U.N. is deeply concerned by the severity of the charges.

Even though two are minors, all three of the accused were held in the high-security division of an adult prison, amid reports that they were interrogated without being appointed legal guardians, Shamdasani said.

“We have made our concerns clear to the Maltese authorities about the treatment of the three young migrants and what we believe to be exaggerated charges against them, and urged them to reconsider the charges,” she said.

There was no immediate comment from Maltese authorities.

Libya is “not a safe port”, Shamdasani said, citing documented killings, torture and arbitrary detention of migrants.

Forcibly returning a migrant rescued at sea to Libya violates the core legal principle of “non-refoulement” that prohibits returns to a place where a person would be at risk of serious human rights violations, she said.

The European Union (EU) and its member states must ensure sufficient search and rescue resources are deployed in the Mediterranean, she said.