Mohammed al-Mabhouh, who was attached to the al-Qassam Brigades, the group's military wing, and, according to Israeli sources, was the lead gun-runner from Iran to Gaza, died in mysterious circumstances in Dubai on 20 January.

On Sunday, however, the Dubai police investigating his death revealed that Mr al-Mabhouh had been poisoned by seven individuals travelling on European passports. Hamas has accused EU states of willingly supplying Israel with the identity documents to aid them in foreign operations.

"We have no doubts that the Mossad is behind the assassination. Israel is the only enemy of our people in the world," Hamas spokesman Ghazi Hamad told EUobserver. "The Mossad will use any means to achieve their goals, often using European passports to enter Arabic countries."

"It could be Mossad, or another party," police chief Dhahi Khalfan told Agence France Presse. "Personally, I don't exclude any possibility. I don't exclude any party that has an interest in the assassination."

On Sunday, Hamas leaders, including Osama Hamdan, the group's external relations chief, and Abu Obeida, spokesman for the al-Qassam Brigades, said they were contemplating the launching of attacks on European soil, which they have not engaged in until now, accusing Israel of "breaking the rules of the game" by targetting the organisation beyond the Israel/Palestine borders.

However, following high-level discussions, the group, according to Mr Hamad, has pulled back from such language.

"It's not easy for Hamas to keep silent, but because its very complicated development, Hamas will discuss this very carefully. We have never thought to move the struggle with Israel outside Palestine.

"But what happened is very dangerous. It means that Israel could do this again in any country, so Israel must pay the price of its crime."

"At the same time, we are not interested to make Europe a playground of conflict between us and Israel. The EU must take crucial actions to stop using Israel to its passports to kill people."