United Nations Special Coordinator for the Middle East Peace Process Robert Serry expressed fears during a visit to the Gaza Strip Wednesday that the tenuous ceasefire reached by Israel and the ruling Hamas Islamist group a year ago was “eroding.”

“I am worried we are seeing more and more signs that the understanding on a ceasefire reached in November 2012 is eroding in both of its main requirements – the end of all hostilities and the opening of the crossings for people and goods,” Serry said. “During the past two months, we have seen more rockets being fired at Israel, border incidents, and Israeli retaliatory operations causing death or injury to civilians. The United Nations condemns the rise in violence, and all parties must act in accordance with international law.”

Serry spoke amid a dramatic uptick in missile attacks from the Strip, with his visit coming one day after Israel launched airstrikes against two targets in Gaza in response to rockets fired out of the Hamas-controlled enclave on Monday that were aimed at southern Israeli towns. At the beginning of the week, the IDF said there had been 33 rocket attacks on Israeli towns and territory from the Hamas-controlled area since the start of 2014.

Israel and Hamas reached a ceasefire agreement in late 2012 following the IDF’s Operation Pillar of Defense, which was aimed at halting missile fire from Gaza at southern Israel.

The UN envoy also decried the social and economic strain caused by Israel’s blockade on Gaza, which has become more sharply felt as smuggling tunnels are closed down by Egyptian security forces. In particular, he said, the flow of construction materials has dwindled significantly.

“The closure of illegal tunnels has not been turned into an opportunity to increase the entry of construction material through legal crossings,” Serry noted. “Even the United Nations construction work has suffered delays as a result of increased closures.”

Serry added that over 20 UN projects have been on hold since November last year due to the restrictions.

“I sincerely hope that the Israeli authorities will fully adhere to their commitment to reopen Gaza for construction materials for UN projects”, he said.

At the end of January, Defense Minister Moshe Ya’alon approved the entry of roughly 1,000 tons of cement and building materials into the Hamas-controlled territory for repairs necessitated by destruction caused during December’s severe storm, in addition to other projects facilitated by UN agencies.

Serry praised the move as a positive step and urged that construction material that does cross legally into Gaza be used for the private sector and not be diverted to non-peaceful uses. The special coordinator also said he hoped the Rafah border crossing between Gaza and Egypt would soon reopen.

Since the ouster of Egypt’s Islamist president Mohammed Morsi in July, the Egyptian military has clamped down on tunneling after it became clear that the subterranean routes also facilitated the transfer of military supplies, equipment and personnel to Islamist militias operating in the Sinai Peninsula.

“Ultimately, only the reunification of Gaza and the West Bank under the legitimate Palestinian Authority, based on the PLO commitments, can pave the way to a durable solution for Gaza, as part of political progress towards peace,” Serry said.