Six weeks after Israeli commandos killed nine pro-Palestinian activists to prevent a Turkish aid ship from reaching the Gaza Strip, tensions are on the rise as a Libyan-sponsored vessel sets out to challenge Israel's naval blockade of the Hamas-controlled territory.

Backed by a charity headed by the son of Libyan ruler Muammar Qaddafi, the ship Amalthea is carrying a cargo of 2,000 tons of food. Organizers say the plan is to reach Gaza within the coming days.

Israel, which is still smarting from the diplomatic uproar over the violent clashes with the Turkish aid ship Mavi Marmara six weeks ago, has sought to enlist foreign governments to convince the aid ship not to challenge the Gaza blockade.

The boat's mission is considered by Israel to be a political provocation made even more suspicious because it is sponsored by the Gaddafi International Foundation for Charity Associations, which is headed by Saif Qaddafi.

Israeli Foreign Minister Avigdor Lieberman discussed the issue with officials in Greece, where the boat got its aid cargo in the past few days. There have also been talks with Egypt, where Israel hopes the ship sponsors will agree to unload their payload.

"The charity that's involved comes from a problematic source,'' says a senior official in the Israeli foreign ministry, which has pleaded its case at the United Nations. "We're not talking about the greatest friend of Israel here.''

Organizers said the ship, which left Greece Saturday, would sail for Gaza despite Israel's efforts to divert the vessel to Egypt.

Israel is trying to block an effort by the United Nations to investigate the clashes on the Turkish ship, the Mavi Marmara, an incident which deepened the diplomatic isolation of the Jewish state and forced it to partially lift a blockade on the flow of goods into the territory of 1.5 million Palestinians for the first time in three years.

Despite the move, there are still severe restrictions on Gaza exports and Palestinians cannot move freely between the West Bank and Gaza. The clash further strained ties with former ally Turkey, which has threatened a downgrade of relations if Israel doesn't apologize.

Israel has said it has no such plans.

Since the May 31 clash, one aid ship, the MV Rachel Corrie, challenged the Israeli blockade, but was peacefully diverted to the Israeli port of Ashdod.

Youssef Sawani, a spokesman for the charity, told Israel Army Radio that the group would not seek a confrontation with the Israeli navy, and would look for another destination to deliver the aid if turned away.