The sanctions imposed by the West on Russia after its invasion of Ukraine are "mad and thoughtless", President Vladimir Putin has said.

Speaking at a forum in St Petersburg, he said "the economic blitzkrieg against Russia had no chance of succeeding from the very beginning".

He said the restrictions were "more harmful" to those who imposed them.

Western nations have been seeking to strike a balance between punishing Russia and protecting their economies.

But speaking at the annual St Petersburg International Economic Forum, President Putin claimed the EU could lose more than $400bn (£326bn) because of its sanctions against Russia.

He said inflation was increasing across the 27-member bloc and the real interests of people in Europe were being sidelined - but did not explain what that meant.

However, Mr Putin's own officials have warned that the Russian economy is suffering serious damage from the sanctions. Central Bank Governor Elvira Nabiullina said on Thursday that "15% of the country's GDP" was threatened by the international response.

Ms Nabiullina also seemed gloomy about the prospects of any imminent recovery, telling delegates at a conference in St Petersburg that "it's obvious to everyone that it won't be as it was before".

"External conditions have changed for a long time indeed, if not forever," she said.

On Friday, the head of the country's largest lender, Sberbank, warned that it could take more than a decade for Russia's economy to return to 2021 levels.

But Mr Putin sought to strike an optimistic tone and also implored Russia's major businesses to keep working in the country, amid reports that an increasing number of business owners were refocusing their efforts on overseas operations.

"Invest here. It's safer in your own house. Those who didn't want to listen to this have lost millions abroad," Mr Putin said.

The 69-year-old leader also addressed fears of a global food crisis triggered by the continuing war in Ukraine, claiming that Russia was capable of significantly increasing its exports of grain and fertilisers. Grain exports alone could rise to some 50 million tonnes, he said.

Ukraine is one of the world's top grain producers along with Russia, but has been unable to send supplies abroad because of a blockade of its Black Sea ports.

On Friday, fierce fighting continued in Ukraine's eastern city of Severodonetsk.

Capturing Severodonetsk - and its twin city of Lysychansk - has for weeks been the key target for Russian troops.

In separate developments on Friday:

• The European Commission backed Ukraine's bid to be given candidacy status to join the European Union - bringing it one step closer to joining the bloc
• UK Prime Minister Boris Johnson held talks in Kyiv with Ukrainian President Volodymyr Zelensky, offering a military training programme that could "change the equation of the war"