US secretary of state Antony Blinken and defence secretary Lloyd Austin have held talks with Volodymyr Zelenskiy, an adviser has told local Ukrainian news outlets. Zelenskiy is expected to use the meeting to appeal for more US military aid.

Russia is planning a “staged referendum in the southern city of Kherson aimed at justifying its occupation”, the UK’s Ministry of Defence has said in its latest intelligence report. “The city is key to Russia’s objective of establishing a land bridge to Crimea and dominating southern Ukraine,” the ministry said.

Igor Zhovkva, a top diplomatic adviser to Zelenskiy, has criticised UN secretary-general Antonio Guterres’ upcoming meeting with Vladimir Putin and Russian foreign minister Sergey Lavrov, saying that Guterres does “not really” have the authority to speak on behalf of Ukraine.

Zelenskiy has tweeted his congratulations to Emmanuel Macron for winning the French presidential election and called Macron “a true friend of Ukraine”.

Dozens of civilians who died during the Russian occupation of the Ukrainian city of Bucha were killed by tiny metal arrows from shells of a type fired by Russian artillery, forensic doctors have said. Fléchettes are an anti-personnel weapon widely used during the first world war.

Latest UNHCR data reveals almost 5.2 million Ukrainians have fled the country. More than 1,151,000 Ukrainians have left during April so far, compared with 3.4 million in the month of March. Beyond that, the UN’s International Organisation for Migration (IOM) estimates more than 7.7 million people have been displaced within Ukraine.

The OSCE, the world’s largest security body, has said it is “extremely concerned” after several of its Ukrainian members were believed to have been arrested in Russian-controlled territories in the country’s east.

In his Easter Sunday message, Zelenskiy said the religious festival “gives us great hope and unwavering faith that light will overcome darkness, good will overcome evil, life will overcome death, and therefore Ukraine will surely win”.

Pope Francis has used the Orthodox Easter weekend to once again appeal for a truce in Ukraine “to ease the suffering of exhausted people”.

Ukraine says hundreds of its forces and civilians are trapped inside the Azovstal steel plant in the city of Mariupol, which Russia has been trying to take for two months. Although Moscow had earlier declared victory in Mariupol and said its forces did not need to take the factory, the Ukrainian authorities say Russian forces have resumed air strikes and are trying to storm the plant.

Turkey’s president Recep Tayyip Erdoğan and Zelenskiy discussed Mariupol during a telephone call. Turkey is ready to give all possible assistance during negotiations between Ukraine and Russia, the Turkish presidency said on Sunday.

The UN has called for an “immediate stop” to fighting in Mariupol so that civilians trapped in the city can be evacuated.