Hamas maintains close ties with the Islamic State-affiliated jihadists in Sinai behind Wednesday’s massive assault on Egyptian troops, Israeli intelligence believes.

Egyptian sources claim that Hamas cares for the Sinai group’s wounded in Gazan hospitals, while the group, which calls itself the “Sinai Province” of the IS-declared “caliphate,” maintains Hamas weapons caches in the Egyptian peninsula, effectively beyond the reach of Israeli air strikes, according to a Thursday report in the Haaretz daily.

Sinai Province is also said to be aiding Hamas in efforts to smuggle weapons into Gaza as part of the Palestinian group’s rearmament program.

Get The Times of Israel's Daily Edition by email and never miss our top stories Free Sign Up

This alliance, defense sources say, is behind the latest acrimony between Cairo and the Hamas rulers of Gaza.

Sinai Province fighters struck Egyptian army outposts in the peninsula Wednesday in a coordinated wave of suicide bombings and battles that left 64 soldiers, 90 jihadists and four civilians dead, according to Egyptian officials. It was the biggest battle in the Sinai since the 1973 Arab-Israeli war. At least 55 soldiers were wounded, they said.

The coordinated Sinai assault focused on the town of Sheikh Zuweid and targeted at least six military checkpoints, security officials said. The jihadists also took soldiers captive and seized weapons and several armored vehicles, they added, speaking on condition of anonymity because regulations did not authorize briefing the media.

The Hamas-IS alliance is not a natural one, the Israeli paper pointed out. Within Gaza, Hamas has been engaged in a low-level shooting war with local IS-affiliated jihadist groups over their firing of rockets into Israel without the Hamas’s government’s approval.

The bitterness between the government of Egyptian President Abdel-Fattah el-Sissi and Hamas precedes the current violence. Hamas is an outgrowth of the Egyptian Muslim Brotherhood, which has been locked in a struggle with the country’s military over control of post-Mubarak Egypt. In 2013, Sissi deposed the elected Muslim Brotherhood president of Egypt, Mohammed Morsi. Hamas backed Morsi in that struggle.

The alliance with Sinai Province appears to be controversial within Hamas as well. It is reportedly being carried out by the group’s military wing, but is opposed by Hamas political leaders, including the Qatar-based Khaled Meshal and Gaza-based Ismail Haniyeh.

In recent weeks, Egypt has eased its blockade of the Hamas-ruled Strip, even opening the Rafah crossing between Gaza and Sinai for brief periods. After Wednesday’s attacks, Cairo appears to be reversing that policy.

AP contributed to this report.