Jerusalem - Israel's internal security agency said on Thursday that it had arrested a senior employee of the international aid group World Vision in the Gaza Strip, accusing him of siphoning millions of dollars of the charity's funds and transferring them to the Islamic militant group Hamas.Mohammed el-Halabi established a "systematic and sophisticated mechanism" to divert up to $50m over the years to the militant group, which rules Gaza, creating fictitious humanitarian projects and doctoring inflated receipts in order to get the funds to Hamas, said the Shin Bet.El-Halabi, whose actions helped Hamas build illegal underground tunnels and purchase weapons for terror attacks, was charged on Thursday, the Shin Bet said.World Vision, a US-based Christian aid group that works in nearly 100 countries, said in a statement on its website that it was "shocked" by the allegations and said it has "no reason to believe" they are true.An Israeli Foreign Ministry official said that Kent Hill, a senior official with the organisation, was holding meetings in Israel over the accusations. Exploiting fundsHamas spokesperson Hazem Qasem called the allegations "lies that may be part of the justification of the blockade imposed by the occupation on Gaza."El-Halabi, who is in his late 30s and from Jebaliya in the Gaza Strip, was arrested in June as he was crossing from Israel into Gaza. The Shin Bet said he underwent Hamas military and organisational training in the early 2000s and was "planted" by the group at World Vision in 2005, where he climbed the ranks to become director of the Gaza branch."He began to conduct security operations for Hamas' military wing which was essentially exploiting the organisation's funds for Hamas' fortification," the Shin Bet said.To divert the funds, the Shin Bet said el-Halabi initiated fictitious projects meant to help farmers, the disabled and fishermen.