AFP reporters saw Zelensky enter the lobby of the luxury hotel hosting the Shangri-La Dialogue, which is attended by defence ministers from around the world.

Zelensky will speak at the security forum on Sunday, according to the International Institute for Strategic Studies, which organised the three-day event.

Zelensky has been touring European nations in recent days to appeal for more military aid for the Ukrainian army, which has been ceding ground to relentless Russian attacks.

The announcement of his Singapore stop followed a US decision to partially lift restrictions on using US-provided weapons to strike inside Russia, which Zelensky hailed as a "step forward".

US President Joe Biden had come under increasing pressure from a desperate Ukraine to ease the curbs, but had resisted for fear doing so could drag NATO into direct conflict or even a nuclear standoff with Moscow.

Germany said Friday it too had given Ukraine permission to fire German-delivered weapons at targets in Russia.

Russian President Vladimir Putin warned Tuesday that there would be "serious consequences" if Western countries gave approval to Ukraine.

Ukraine is struggling to hold back a Russian ground offensive in the Kharkiv region, where Moscow recently made its largest territorial gains in 18 months.

With Russia's war against Ukraine in its third year, Ukrainian soldiers are exhausted and outgunned.

Many allies of Kyiv remain uneasy about the prospect of sending Western troops to Ukraine.

In February, French President Emmanuel Macron sparked an uproar among NATO members when he refused to rule out sending troops to Ukraine.

Zelensky has visited Spain, Sweden, Portugal and Belgium in recent days as he seeks more weapons and aid for his struggling military, and to drum up support for a peace summit due to be held in Switzerland this month.

Sweden on Wednesday pledged 13.3 billion kronor ($1.25 billion) in military aid to Ukraine.

The Scandinavian country, which formally joined NATO in March, will donate a range of military supplies, including ASC 890 surveillance aircraft, Rb 99 medium-range air-to-air missiles and artillery ammunition, and its entire fleet of PBV 302 armoured tracked personnel carriers.

Russia fired a combined 100 missiles and drones at Ukraine in an overnight barrage targeting energy sites across the country, Ukrainian officials said on Saturday.

Russia has launched hundreds of aerial attacks at Ukraine's power facilities throughout the war, causing significant damage and energy shortages as Ukraine's stretched air defences struggle to repel waves of drones and missiles.