A group of pro-Palestinian activists, including a Nobel Peace laureate from Northern Ireland, are aboard an aid ship heading for the Gaza Strip, and they expect to arrive there late Friday or early Saturday despite Israel's insistence that it will not allow any vessel to breach its blockade, according to multiple reports.

The MV Rachel Corrie, a 1,200-ton converted merchant ship purchased by pro-Palestinian activists, set off Monday from Malta, Reuters reports. The vessel is named after an American woman killed in the Gaza Strip in 2003.

The ship left for Gaza on the day Israeli commandos stormed a Turkish-backed aid vessel purportedly carrying humanitarian aid to the Hamas-governed territory, igniting a confrontation that left nine people dead and launched an international firestorm of protest.

"We're on our way to Gaza," crew member Derek Graham told Reuters by phone. "Everybody was very upset at what happened. Everybody has been more determined than ever to continue on to Gaza."

Graham said the ship is carrying 15 activists -- including Nobel Laureate Mairead Corrigan-Maguire -- and was roughly 280 miles from Gaza on Thursday. Former U.N. Assistant Secretary-General Denis Halliday is also on board the ship, the Irish Times reported.

Israel has offered to escort the vessel and deliver the civilian aid items aboard, and it says Egypt is prepared to do the same. But Graham said he was concerned that not all of the cargo -- including medical equipment, school supplies and cement -- would be delivered. Israel maintains that cement can be used in rocket launchers, and not just for building construction.

Israeli Foreign Minister Avidgor Lieberman said Israel would not allow its Gaza blockade to be breached, meaning the ship would have to be boarded and inspected before it was allowed to pass.

"No ship will reach Gaza," he told Israel Radio. "The Rachel Corrie will not reach Gaza."

Graham said he'd consider an escort from the United Nations.

"We're willing to let the U.N. come and inspect the cargo," he told Reuters. "We will accept an escort from the U.N. … Our communication is pretty limited but we would hope there would be people working on that as we speak."

Halliday has also called for an escort into Gaza.

"We want to emphasize that our aim is not provocation but getting our aid cargo into Gaza," Halliday told the Irish Times. "We all remain in good spirits."

A maritime blockade remains in effect off the coast of Gaza, as Israel is currently in a state of armed conflict with Hamas, which has repeatedly bombed civilian targets in Israel with weapons that have been smuggled into Gaza via the sea, according to Israel's Ministry of Foreign Affairs.

Robert Margolis, an expert in international maritime law based out of Vancouver, Canada, said no boats, including civilian and enemy vessels, can enter a blockaded area when a maritime blockade is in effect.

"Israel is acting under the customary maritime law of blockade," Margolis told FoxNews.com. "You're allowed to do that; they declared a blockade over a port."

Margolis said Israel is acting "completely" within guidelines of blockades under international maritime law. Any vessel that violates a blockade, including the Rachel Corrie, may be captured, boarded or even attacked under international law.

"If [the Rachel Corrie] insisted on going all the way to Gaza, then the Israelis have the right to board it, not to sink it," said Margolis, citing guidelines regarding appropriate use of force. "Rather than sink it, Israeli commandos would board the vessel."

Once a blockade is established, Margolis said it must be enforced.

"You can't have a blockade where you don't try and stop every vessel," he said. "Blockades fail from non-enforcement. The law of blockades require enforcement; there's no such thing as a paper blockade."

Meanwhile, Iran pushed for sanctions against Israel and asked that nations sever diplomatic ties with the Jewish state, calling for an international flotilla of hundreds of ships to descend upon Israel's shores.

"We need to dispatch hundreds of humanitarian vessels to Gaza under the flag of as many countries as possible," Iran's U.N. ambassador, Mohammad Khazaee, said in a statement to the Organization of the Islamic Conference.

All of the nine activists killed in Monday's raid died from gunshot wounds -- some from close range -- according to initial forensic examinations done in Turkey after the bodies were returned, NTV television reported, citing unidentified medical sources.

Israel maintains that the commandos used their pistols only as a last resort after they were attacked, and it released a video showing soldiers in riot gear descending from a helicopter into a crowd of men with sticks and clubs. Three or four activists overpowered each soldier as he landed, the video shows.

Israeli officials say their military is investigating the raid and that they are capable of conducting a credible review.

"It is our standard practice after military operations, especially operations in which there have been fatalities, to conduct a prompt, professional, transparent and objective investigation in accordance with the highest international standards," Israeli government spokesman Mark Regev said.

FoxNews.com's Joshua Rhett Miller and The Associated Press contributed to this report.