(CNN) -- Israel is easing restrictions on the Palestinian territory of Gaza, allowing building materials for the private sector to enter the densely populated sliver of land for the first time since Hamas took control there in 2007.
Trucks carrying tons of building materials for the renovation and rehabilitation of 10 private Palestinian-owned factories have been flowing in since Tuesday. Over the last four years, only limited amounts of building materials were permitted, and only for international projects.
Sami Mshasha, a spokesman for the U.N. Relief and Works Agency for Palestine Refugees in the Near East, said he welcomed the development. But Mshasha said that what is being done is "too little" and that the Gaza factory owners need more than just building materials to restart their businesses.
"There is a need for spare parts in order to have sustained economic impact," Mshasha said.
The Palestinian Authority, the Israel Defense Forces, the United Nations, and the Quartet worked on the plan. The Quartet is the Middle East peace initiative of four international entities -- the United States, the United Nations, Russia, and the European Union.
Sari Bashi -- the director of Gisha, an Israeli nongovernmental organization that advocates for Palestinian rights of movement and access -- called on the Israeli government to lift all restrictions on the import of building materials to Gaza.
"Any security concerns are completely irrelevant because militants who want to buy cement can," Bashi said. "The controls harm the private sector and the Palestinian economy and not Hamas."
But Guy Inbar, spokesman for the Israeli military's Coordinator of Government Activities in the Territories, said the restrictions are in place for security reasons and there is no wish for the materials to end up in Hamas' hands.
Israel is concerned that the militant Hamas group will use materials for the purpose of attacking its territory. Israel, the United States and the European Union consider the Islamist group a terrorist organization.
Israel had enacted a ban on the import of building materials after the Hamas takeover of Gaza in 2007. But after nine people were killed during an Israeli raid on a Gaza-bound aid boat last year, the government relaxed some of the import restrictions.
The export of agricultural produce to Europe is supposed to start in the coming weeks.
Inbar said Israel is committed to Gazan economic projects, part of a package of gestures agreed to in February by Israeli Prime Minister Benjamin Netanyahu and Quartet envoy Tony Blair.