Neither Israel nor Egypt provided evidence for their claims. Questions remain, including how the rockets would have been smuggled into Gaza, largely cut off from the world by a border blockade enforced by Israel and Egypt.
Israel's government has used the interception to bolster claims that Iran remains dangerous and that the world powers should break off negotiations with Tehran over the country's nuclear program.
Defense Minister Moshe Yaalon alleged Sunday that the weapons shipment "uncovered the true intentions of the regime in Tehran, a regime that is sly, dangerous and without restraint, that continues to train, finance and arm terror groups in the Middle East and beyond and whose aim is destabilize the area and the whole world."
In a further attempt to highlight Iran's alleged role in arming militants, Israeli Prime Minister Benjamin Netanyahu planned to hold a news conference Monday in Israel's Red Sea port of Eilat, where the Panama-flagged KLOS C docked under Israeli navy escort Saturday.
Israel's military said Sunday that 40 rockets of the type M-302, with ranges of up to 160 kilometers (100 miles) or enough to reach Israel's main cities were unloaded from the vessel. In addition, the military said it counted 181 mortar shells on the ship, along with some 400,000 rounds of ammunition.
It remains unclear to what extent the intercepted rockets would have raised the threat level against Israel.
Gaza's ruling Hamas and the smaller group Islamic Jihad already possess thousands of rockets, though apparently with a shorter range. During eight days of fighting in 2012, armed groups from Gaza fired 1,500 rockets into Israel, including several that reached the outskirts of Jerusalem and Tel Aviv.
From the north, the Iranian-allied Lebanese guerrilla group Hezbollah also is believed to have thousands of rockets and missiles that could reach deep into Israel.
Israel intercepted the cargo ship last Wednesday, about 100 miles (160 kilometers) off the coast of Sudan. Israel has said the raid was a result of months of painstaking intelligence work.
Israeli officials said the rockets were flown from Syria to Iran months ago, then shipped from Iran's Bandar Abbas port to Umm Qasr, Iraq, before being loaded onto the KLOS C, a civilian ship destined for Sudan.
From there, Israeli officials said they were to be smuggled overland through Egypt to Gaza a route that has been used in the past.
The Egyptian security official said he believed the vessel's final destination was close to Ras Mohammed, a nature reserve in the Sinai.
Since last summer, the Egyptian military has destroyed or sealed many of the dozens of smuggling tunnels under the Gaza-Egypt border. However, the official said he believes some of the rockets could have made it through the tunnels despite the crackdown.
Iran, as well as Hamas and Islamic Jihad, have denied any involvement with the shipment.
Associated Press writer Ashraf Sweilam in Sharm El-Sheikh, Egypt, contributed to this report.