Israeli troops are seen near the southern Israeli border with Gaza, on March 18, 2025. [Photo/Xinhua]

Israel on Wednesday expressed "sorrow" over the death of a Bulgarian United Nations staff member in strikes on UN guesthouses in Gaza's Deir al-Balah but said an initial investigation found no Israeli involvement in the incident.

The United Nations said the staffer, employed by the UN Office for Project Services (UNOPS), was killed when two UN facilities were hit. Five other personnel sustained serious injuries.

Israeli Foreign Ministry spokesperson Oren Marmorstein said a preliminary inquiry "found no connection" between Israeli military operations and the strike.

"The circumstances of the incident are being investigated," he said, adding that Israel facilitated the evacuation of the victim's body and the wounded from the site.

The injured would receive treatment in Israeli hospitals, he said in a post on social media platform X.

UN Secretary-General Antonio Guterres condemned the attack as a violation of international law. "All UN premises' locations are known to parties to the conflict, who are obligated to protect them," a UN spokesperson said in a statement.

Guterres extended condolences to the victim's family, noting that the death brought the number of UN staff killed in Gaza since Oct. 7, 2023 to at least 280.

"These premises were well known by the Israel Defense Forces (IDF) and they were 'deconflicted'," UNOPS chief Jorge Moreira da Silva said, adding that it was clear UN personnel were inside at the time.

"This was not an accident, this was an incident," he told reporters, saying additional information was being gathered.

Earlier on Wednesday, the Israeli military denied targeting the compounds. "Contrary to reports, the IDF did not target a UN facility in Deir al-Balah," it said in a statement.

The incident occurred as Israel renewed military operations in Gaza, which officials say are aimed at Hamas militants. Gaza health authorities reported more than 400 Palestinian deaths since Tuesday, including at least 170 children and 80 women, after Israel resumed strikes following a weeks-long ceasefire that began on Jan. 19.

Israel's military said the operations were intended to "eliminate Hamas threats" and would continue "until strategic objectives are achieved."