Moscow has stepped up its aerial attacks after Ukraine's offensive in Russia's Kursk region, which caught Russian troops by surprise.

"It's not up to us," said Andrés Manuel López Obrador when asked by press

Moscow's defence ministry said it had rushed its troops and aviation units to the border in southwestern Kursk region after a morning raid by Ukrainian units -- the latest such attack throughout the conflict.

The announcement came as Ukrainian President Volodymyr Zelensky visited special forces in the border region of Kharkiv, where Moscow's forces launched a surprise ground offensive in May but failed to make any major breakthrough.

Such missiles, which can travel between 500 and 5,500 kilometres (300-3,400 miles), were the subject of an arms control treaty signed by the US and the Soviet Union in 1987.

Moscow is Syria's most important ally, having effectively saved Assad's government through its military intervention in 2015 during a civil war.

With its castle, medieval tower and river-side beach, the western Ukrainian tourist town of Starokostiantyniv doesn't seem an obvious target for Russian missile and drone strikes.

Zelensky said on Monday that Russia "should be" represented at a second summit on the Ukraine conflict, following high-level talks last month in Switzerland that Moscow did not attend and heavily criticised.

Kicking off three days of events for the 32-nation alliance with a celebration Tuesday evening, Biden announced a new air defense system for Kyiv and urged unity against Russian President Vladimir Putin, who launched the Ukraine invasion in 2022.

Russia is a key supplier of cut-price oil and weapons to India, but its isolation from the West and growing friendship with China have impacted its time-honoured partnership with New Delhi.

When Russian paramilitary chief Yevgeny Prigozhin sent his Wagner mercenaries charging towards Moscow last year in a short-lived rebellion, President Vladimir Putin looked weak and vulnerable.

The targeted aerial barrages over recent months have crippled Ukrainian electricity generation capacity and forced officials to impose rolling blackouts and import supplies from neighbouring EU states.

Last week, the United States unveiled fresh sanctions against 300 targets in and outside Russia.

Putin is scheduled to touch down on Tuesday night for his first trip to the isolated nation in 24 years, with a confrontation between North and South Korean troops on their shared border highlighting regional security tensions.

Washington sees the exercises as a response to American support for Ukraine and larger drills with NATO allies

The warning came as French President Emmanuel Macron said Kyiv should be allowed to "neutralise" Russian military bases from where Kremlin troops are firing missiles into Ukraine, and as President Volodymyr Zelensky urged the world not to tire of the war.

On Thursday, Putin arrived in China on a two-day visit as Moscow is seeking more support from President Xi Jinping for the war effort in Ukraine following multiple rounds of Western sanctions.

Putin's war in Ukraine, which began with the February 2022 invasion, is believed to have killed hundreds of thousands of people and has made the Russian president a pariah in much of the world.

However, his handling of the assault against Ukraine was criticized by many in Russia and his reputation was further hit by recent corruption accusations against one of his deputies.

Russian President Vladimir Putin will address the annual Victory Day parade in Moscow on Thursday, an event he hopes will rally patriotism as his forces advance in Ukraine.

Russia's troops are advancing in the eastern Donetsk region as Kyiv awaits the arrival of much-needed US weapons that it hopes will stabilise the fragile front lines.

Russia and China have in recent years ramped up contacts, and their strategic partnership has only grown closer since the invasion of Ukraine.

All four gunmen in the deadly concert hall attack Friday night in Russia's Crocus City have been taken into custody and were remanded into pre-trial detention through May 22.

Questions have swirled over how the country's powerful security apparatus was unable to thwart the deadliest attack in Russia in two decades -- even as Western counterparts issued public and private warnings just two weeks prior.

Over two years into Moscow's all-out war against its neighbour, Kyiv's troops are struggling to hold back the Russian army as Western support fails to keep pace with the fighting.

Biden said the stopgap shipment of missiles, shells and ammunition for Kyiv was "not nearly enough" and would run out in a couple of weeks.

Victory in the March 15-17 contest will allow him to stay in the Kremlin until at least 2030, longer than any Russian leader since Catherine the Great in the eighteenth century.

The ceremony will take place two weeks after Navalny died in an Arctic prison, amid pressures denounced by his team who accuse Russian President Vladimir Putin of murdering his top critic.

For the Ukrainian troops holding Russian forces from cities like Kostyantynivka, the task is becoming harder as their resources and stamina ebb.

Former US President George W. Bush believed he had a "sense of his soul".