Ayelin Mengistu pleaded for his son in Geneva
Ayelin Mengistu pleaded for his son in Geneva Permanent Mission of Israel to the United Nations Office at Geneva / Handout

The parents of an Israeli man believed to be held by Hamas in Gaza since 2014 travelled to Geneva this week to demand international action to help bring him home.

Avera Mengistu, a 33-year-old Israeli of Ethiopian descent, is depressed and suffering from mental problems since the death of his older brother when he crossed into Gaza five years ago.

He was filmed by an Israeli security camera climbing the frontier fence with the Gaza Strip in September 2014.

Israel's defence ministry determined he was being held by Hamas, but the Islamist movement governing Gaza has to date provided no information about his whereabouts or condition.

'Plain cruelty'

"This is just plain cruelty," Avera's mother Agarnesh told AFP, speaking through an interpreter.

With tears trickling down her face, she implored Hamas to "provide any sign of life".

"Is he alive or not? Does he eat? Does he receive medical care? Are they taking care of him?" she asked. After five years in the dark she was consumed by worry, she said.

"I cannot sleep, I cannot work, I cannot rest."

She and her husband Ayelin, who live in the southern city of Ashkelon near the Gaza border, said they had travelled to Geneva to meet with diplomats and UN officials to ask why the international community was not doing more to help Avera, one of their 10 children.

They said countries that provide aid to Gaza should be able to put pressure on Hamas.

"Please help us! He is a sick person," Agarnesh said.

The parents met with UN rights chief Michelle Bachelet on Wednesday.

"She promised she would do whatever she can," Aviva Raz Shechter, Israel's ambassador to the UN in Geneva, told AFP.

Raz Schechter, who accompanied the family at several meetings in Geneva, said Bachelet had acknowledged that she did not have direct contact with Hamas, but had said she would "try to find ways to receive information."

They also confirmed that they had recently met with Palestinian president Mahmoud Abbas, who Ayelin Mengistu said had promised to "do everything to… help you, to try to bring your child to you."

But "he did not bring any specific information," he said through a translator.

Hamas has never officially confirmed it is holding Mengistu or another mentally ill man -- Arab-Israeli Hisham Al-Sayed -- but videos the group has published on social media have included both their images.

The Islamist group, which took control of Gaza in 2007, has not released any details on their condition or allowed rights groups to visit them.

Israel does not allow its citizens to enter Gaza, partly over fears that they may be used as bargaining chips to demand concessions, including the release of prisoners.

In 2011, Israel released more than 1,000 Palestinian prisoners in exchange for soldier Gilad Shalit, who had been held by Hamas for five years.