Mr Fletcher plans to press for stopping the atrocities in the Kordofan and Darfur regions.
Local officials reported that nine had been killed in the twin drone strikes.
Twenty villages in eastern Sudan have reportedly been “destroyed” after floodwaters burst through a major dam, according to UN humanitarians.
The WHO spokesperson added that only 14 hospitals are still functioning in Gaza.
UN Day on October 24 marks the anniversary of the entry into force in 1945 of the UN Charter – the day the organisation officially came into being.
Over 423,000 people have already been displaced, of whom more than 270,000 have taken refuge in UNRWA shelters.
UN humanitarians said no fewer than 870,000 people who fled abroad since the Russian invasion of Ukraine on February 24 had returned home.
UN has warned that the exodus of millions of Ukrainians from their country following the Russian invasion could overwhelm neighbouring countries.
