A Palestinian engineer who is believed to have been abducted from Ukraine by the Israeli secret service, Mossad, denied he had done anything wrong when he appeared in court on Thursday .

Prosecutors asked the court in Petah Tikva in central Israel to allow the continued detention of Dirar Abu Sisi for five days after which he would be charged. No charges have been made public.

Abu Sisi, who has not been seen since his abduction on 19 February, told the court that he had been abducted and that he denied all allegations against him. Referring to an Israeli solider abducted by Hamas in 2006, he said: "I don't know anything about Gilad Shalit. I don't know anything. I'm an engineer."

Reports suggest Abu Sisi was taken forcibly from a train in Kharkov then flown to Israel. It later emerged that he was being held in Ashqelon prison in southern Israel.

Abu Sisi works as an engineer for a power company in the Gaza Strip and is married to Veronika, a Ukrainian national with whom he has six children. His family said that he was in the Ukraine to apply for citizenship to enable his family to leave Gaza.

While no charges have been made against the engineer, the German magazine Der Spiegel claimed that he was kidnapped because he had knowledge of the whereabouts of Gilad Shalit. However, Ehud Barak, Israel's defence minister, said there was no direct link between Shalit and Abu Sisi.

"He didn't organise the abduction or guard Shalit but he is a person with intimate internal information on Hamas. This has value," he told Israel army radio.

Smadar Ben Natan, Abu Sisi's lawyer, said that she had general knowledge of the charges against her client which were out of proportion to the efforts made to bring him to Israel. "He is not a member of Hamas. He has a public position in the electricity distribution company. No one has said he is an essential person to any organisation, only that he has information. It's impossible to live in Gaza and not have some knowledge of Hamas," she told the Guardian.

In a telephone conversation made public on Thursday, Noam Shalit, the father of the Israeli soldier held in Gaza, asked Veronika Abu Sisi to help get his son released. She told him: "Your son is the same as my husband. Your son was kidnapped without foundation and my husband was kidnapped without foundation."

In Kiev, Mohammed al-Assad, the Palestinian envoy in Ukraine, told a news conference that Abu Sisi "was not a member of any organisation".

Describing Abu Sisi's disappearance as a "terrible act of piracy", Assad urged the Ukrainian authorities to put pressure on Israel to ensure his safe return to Ukraine.

"At the moment there is no proof that Mossad officials seized him, but the fact is that he is there," Assad said. "We consider his disappearance and relocation ... as an international crime for which someone must bear responsibility."

The abduction of Abu Sisi happened one year after suspected Mossad agents killed Mahmoud al-Mabhouh, a member of Hamas, in his hotel room in Dubai. Dubai police issued arrest warrants for at least 26 agents who were travelling with British, Irish and other European passports. It later emerged that some of the passports had been copied from Israeli citizens who had dual nationality.