A Palestinian engineer who vanished on a Ukrainian train and mysteriously turned up in an Israeli prison made his first public comments Thursday, accusing the Jewish state of kidnapping him "for no reason" and saying he had no information about an Israeli soldier held captive in the Gaza Strip.

Dirar Abu Sisi spoke as he entered an Israeli court in the central city of Petach Tikva for a brief hearing that extended his arrest until next Tuesday. His lawyer said authorities informed her that he will be indicted on unspecified charges next week.

Abu Sisi's case has been clouded in secrecy because of an Israeli gag order barring publication of most details. He disappeared in the early hours of Feb. 19 after boarding a train in the Ukrainian city of Kharkiv. His family has accused Israel's Mossad spy agency of abducting him.

As he entered the courtroom, Abu Sisi, 42, told reporters he was just a power plant engineer in Gaza and that "Israel kidnapped me for no reason." He also said he knew nothing about Sgt. Gilad Schalit, an Israeli soldier captured in Gaza in June 2006 by Hamas-linked militants.

Germany's Der Spiegel magazine speculated this week that Israel might have seized Abu Sisi to try to wrest information about the fate of the soldier. Militants have allowed no access to Schalit since his capture, releasing only a brief videotaped statement from him in October 2009.

Abu Sisi's Israeli lawyer, Smadar Ben-Natan, said Thursday that authorities informed her he will be indicted next week but gave no details on the charges.

On Wednesday, Israeli Prime Minister Benjamin Netanyahu spoke about the case for the first time, saying that Abu Sisi belongs to Hamas, the violently anti-Israel group that rules Gaza. He said Abu Sisi relayed important information but did not elaborate.

Ben-Natan denies Abu Sisi is a Hamas loyalist and his Ukrainian wife alleges Israeli agents kidnapped him to sabotage a key power plant in Gaza where he worked. She has said he was in Ukraine to apply for citizenship.

Fellow engineers and neighbors told The Associated Press that Abu Sisi was a Hamas supporter, based on his senior position at the Hamas-controlled power plant.

He surfaced in an Israeli prison days after he disappeared in Ukraine. Israel confirmed it was holding him only a month after his disappearance.

The Gaza-based Palestinian Center for Human Rights, which sent one of its lawyers to visit Abu Sisi in jail, said he reported that he was dragged out of his sleeper car, hooded and handcuffed by Israeli agents and forced on a plane bound for Israel.

On Thursday, the Palestinian ambassador to Ukraine, Mohammed Alassad, accused Israel of "piracy" in the Abu Sisi case, calling it "an international crime that must be punished."

Speaking through a translator in Kiev, Alassad said Palestinian authorities were still waiting to hear from the Ukrainian government how Dirar Abu Sisi ended up in Israel.

The Ukrainian government has said it was not involved in the operation and was waiting for an official Israeli explanation.