(AFP) - European leaders vowed to remain united in the face of Russia's aggression against Ukraine and Moldova on Thursday, staging a strategy summit on the continent's political frontline.

As another deadly missile barrage hit Kyiv, and Moscow claimed to have repulsed a Ukrainian attempt to "invade" Russian soil, 45 leaders met in vulnerable Moldova.

The venue for the European Political Community summit, the Castle Mimi wine estate in the east of the country, lies only 20 kilometres (12 miles) from the border with war-torn Ukraine, adding to the symbolism of the talks.

Ukraine's President Volodymyr Zelensky arrived first, making the short journey to his smaller neighbour while his own capital Kyiv counted the cost of another night of Russian strikes: three dead, including a child.

President Maia Sandu welcomed the leaders one by one under a clear blue sky patrolled by NATO early warning aircraft, hoping to boost Moldova's stature as a small pro-Western democracy seeking European support and protection.

"Ukrainians are fighting for freedom, European values and the future of our continent," she said.

And she dubbed the summit, "a clear expression of our unity, strength and determination to act together as a single family."

Zelensky, however, warned that the ongoing debate over how and how quickly to follow up on Ukraine's ambitions to join both the EU and NATO would embolden Russia.

"We must remember that every doubt we show here in Europe is a trench that Russia will definitely try to occupy," he said, calling for Europe to extend immediate security guarantees and "clear invitations" to NATO membership.

Both Kyiv and Chisinau hope to start EU membership talks this year, despite Moscow's ongoing invasion of Ukraine and alleged attempts to undermine Moldova's sovereignty.

- 'Security guarantees' -

The EPC summit was also being held less than 10 kilometres from the breakaway Moldovan region of Transnistria, which is occupied by Russian "peacekeepers".

It was held under tight security, with NATO's AWACS surveillance planes flying over neighbouring Romania extending cover over the tiny former Soviet republic's air space.

The European Political Community groups 47 European countries from inside and outside the EU -- and excludes Russia and Belarus.

Only tiny San Marino and Turkey, whose newly-elected president Recep Tayyip Erdogan is preparing for his inauguration, failed to send a leader to the talks.

It is a forum for strategic debate and addressing regional crises and -- for some members -- a potential steppingstone to full EU and or NATO membership.

"We must also think of a wider Europe," France's President Emmanuel Macron, who first promoted the idea of forming the EPC, told reporters in Bratislava on the eve of the summit.

"We must think of our Europe not simply from a security point of view within the framework of NATO and not simply within the framework of the European Union."

The Moldova summit also came as NATO ministers, including US Secretary of State Antony Blinken, met to discuss the agenda of the alliance's next summit.

The NATO summit in Vilnius on July 11 will debate how formal a promise to give Kyiv on how and when to join the alliance, but in the interim Europe is keen to show support.

- 'Rocket barrage' -

Macron said the allies should find a way to offer "tangible and credible security guarantees to Ukraine" while the eventual questions of EU and NATO membership are pending.

Estonia's Prime Minister Kaja Kallas went further.

"In the long term, the only security guarantee that really works is to end the grey zones in Europe, which means that the only security guarantee really is NATO," she said.

During the summit, Macron and Germany's Chancellor Olaf Scholz will meet between Armenian Prime Minister Nikol Pashinyan and Azerbaijan's President Ilham Aliyev.

Yerevan and Baku have fought for decades over the disputed territory of Nagorno Karabakh, but have both been invited to the EPC as Washington and Brussels push for a peace deal.

Another long-standing European conflict, the standoff between Serbia and Kosovo, will be on the agenda, with leaders from Pristina and Belgrade under pressure to dial down tensions.

While the talks took place, fighting continued in Ukraine, and the governor of the Russian region of Belgorod said rockets fired across the border had wounded eight people.

Moscow's defence ministry, meanwhile, said it had "thwarted" an attempted incursion into southwestern Russia by what it said was two Ukrainian motorised infantry companies reinforced with tanks.

© Agence France-Presse