The UN chief has added his strong condemnation of Russian strikes overnight into Sunday targeting Kyiv and other Ukrainian cities which killed dozens - including children - and damaged civilian infrastructure.
Secretary-General António Guterres said it marked a "further escalation" of the conflict.
Authorities reported more than 80 civilian casualties, including a national non-governmental organization (NGO) worker and her two-month-old son in Kyiv.
Other affected cities included Zaporizhzhia, Odesa, Chernihiv, Kharkiv, Kremenchuk, Kryvyi Rih and Kherson. Energy infrastructure was also hit, causing temporary power and water outages ahead of winter, with repair crews working to restore services.
"Attacks against civilians and civilian infrastructure violate international humanitarian law. They are unacceptable and must end immediately," UN Spokesperson Stéphane Dujarric said Monday at the regular news briefing in New York.
"The Secretary-General reiterates his call for a full, immediate and unconditional ceasefire as a first step towards a just, comprehensive and sustainable peace in Ukraine, one that fully upholds Ukraine's sovereignty, independence and territorial integrity, in line with the UN Charter , international law and relevant UN resolutions," he added.
Meanwhile, humanitarian support continues. On 5 September, UN agencies and partners delivered medical kits and hygiene supplies to roughly 1,000 people in several Donetsk villages, marking the tenth convoy to the region this year.
Gaza: Civilian toll continues to climb
Civilians in Gaza continue to face mounting deaths, displacement and famine as hostilities continue, with UN agencies warning that the window to prevent widespread starvation is closing.
According to local health authorities, some 67 people were killed and 320 injured in the past 24 hours, Mr. Dujarric said, adding that since the end of the ceasefire in mid-March nearly 12,000 people have died amid repeated displacement and attacks.
"We continue to condemn all killings of civilians," he said.
The humanitarian situation remains dire. The UN aid coordination office, OCHA , noted urgent needs for food, water and shelter.
"Our colleagues remind us that over 80 per cent of Gaza is either under displacement orders or within militarized areas," Mr. Dujarric added.
The Gaza Ministry of Health reported that over 100 people, a quarter of them children, have died from malnutrition since famine was confirmed in Gaza governorate.
Humanitarian operations remain heavily constrained.
Only 11 of 24 coordinated missions were facilitated on Sunday, including fuel collection at crossings, while others were denied or cancelled. Humanitarians were able to distribute water in northern Gaza and collect food shipments from Kerem Shalom, Karem Abu Salem and Zikim crossings.
UN peacekeepers in DR Congo continue to protect population against 'grave danger'
Hundreds of thousands of people fleeing conflict in the eastern Democratic Republic of the Congo (DRC) continue to be protected against "grave danger" by United Nations peacekeepers, according to the head of UN Peace Operations.
Jean-Pierre Lacroix was speaking at the end of a mission to the DRC, where he visited the troubled Ituri and North Kivu regions.
Mr. Lacroix emphasised that hundreds of thousands of Congolese people, including displaced people, rely on the UN peacekeeping mission, MONUSCO for daily protection, particularly in the areas of Fataki and Beni, in North Kivu, where joint operations with the Congolese armed forces continue against armed groups.
