"We would be very grateful to Ukrainian and Israeli government agencies for giving us more detailed information," spokesman for the UN Office's department in Ukraine Maksym Butkevych told Interfax-Ukraine.
"Veronika Abu Sisi informed us on February 23 about the disappearance of her husband Dirar Abu Sisi," he said.
The Palestinian is registered with the UN Middle East agency for aiding Palestinian refugees, he said, adding that if he is outside the territory under the agency's jurisdiction, he automatically comes under the mandate of the Office of the UN Commissioner for Refugees.
"Therefore, when a report arrived about Mr. Abu Sisi's disappearance, we turned to the Ukrainian Interior Ministry to for more information and to find out his likely whereabouts," Butkevych said.
"Unfortunately, no information has arrived from the Interior Ministry," he said.
"Then we got information from our representatives in Israel, who had received a confirmation from Mr. Abu Sisi's defense lawyer that he was in jail in Israel and that the date of his arrest coincided with his disappearance - February 19, as stated by his wife," he said.
Butkevych said it was not known how the Palestinian had disappeared in Ukraine and re-appeared in Israel. But the UN is mostly concerned about whether he traveled to Israel on his own or by force, he said.
"And of course, we are concerned that if he was forced into Israel, law may have been violated and the Palestinian's human rights abused," Butkevych said.