UN Secretary-General Antonio Guterres has arrived in Kyiv ahead of talks with Ukrainian President Volodymyr Zelenskyy.

• UN chief in Kyiv for talks with President Volodymyr Zelensky
• UU says Russia's gas move is energy 'blackmail'
• Putin warns other nations against intervention
• Kyiv conceded that Russian forces had made gains in the east

This article was last updated at 9:55 GMT/UTC

Germany top buyer of Russian fuel, study says

Figures compiled by an independent research group show that Germany has been the biggest buyer of Russian energy in the first two months since the war in Ukraine began.

A study published by the Centre for Research on Energy and Clean Air calculates that Russia has earned €63 billion ($66.5 billion) from fossil fuel exports since February 24.

Researchers used data on ship movements, real-time tracking of gas flows through pipelines and estimates based on past monthly trade.

They worked out that Germany alone paid Russia about €9.1 billion for fossil fuel deliveries in the first two months of the war.

Germany has faced strong criticism for its reliance on Russian gas and oil despite allies' warnings that this could prove a danger to European security.

According to the study — titled "Financing Putin's War on Europe — the second biggest importer of Russia's fossil fuels since the invasion began is Italy (€6.9 billion), followed by China (€6.7 billion).

UN chief in Kyiv for talks

United Nations Secretary-General Antonio Guterres has arrived in Kyiv to meet Ukrainian President Volodymyr Zelenskyy.

The UN head is also set to meet Foreign Minister Dmytro Kuleba and visit an undisclosed location outside the capital.

Earlier in the week, Guterres met Russian President Vladimir Putin in Moscow, where the two were said to have discussed the possible evacuation of the besieged Azovstal steel complex in the city of Mariupol.

The pair were said to have agreed "in principle" to the United Nations and International Red Cross participating in the evacuation.

UN officials reportedly held follow-on discussions with authorities in Moscow and Kyiv "to develop the operational framework for the timely evacuation of civilians."

It's estimated that 2,000 troops and 1,000 civilians are sheltering in bunkers underneath the wrecked plant.

After his meeting with Putin, Guterres traveled to Poland and on to Kyiv by train.

Blasts knock out Russian TV in Kherson

A series of explosions were reported late Wednesday near a television tower in the southern Russian city of Kherson.

Both Ukrainian and Russian news organizations reported that the series of explosions temporarily knocked Russian channels off the air.

Russian state news agency RIA Novosti said the broadcasts had resumed. It also said the Russian channels had begun broadcasting from Kherson last week.

Kherson has been occupied by Russian forces since early in the war.

Russia has been determined to strengthen its control over the city, but residents have continued to protest the occupation with demonstrations on the street.

Ukraine's prosecutor general on Wednesday said Russian forces had used tear gas and stun grenades to disperse a pro-Ukraine rally in the occupied city.

Summary of Wednesday's events in the Ukraine-Russia crisis

The European Union condemned Russia's halting of gas supplies to member states Bulgaria and Poland as "blackmail."

The two countries were supplied with gas by their EU neighbors after Russia's state energy giant Gazprom turned off the taps.

Gazprom had announced the halt of gas to the countries after not receiving payment in rubles — a stipulation made by Moscow in response to sanctions.

The EU Commission also proposed a one-year suspension on all imported goods from Ukraine that are not already subject to an existing free trade deal.

Russian President Vladimir Putin issued a warning, saying intervention by Western forces would be met with a "lightning-fast" military response.

The Russian leader referred to weapons that "no one else can boast of having," apparently referring to Moscow's ballistic missiles and nuclear arsenal.

Meanwhile, Moscow claims it carried out a missile strike in southern Ukraine to destroy a "large batch" of weapons it says were supplied by the West.

Kyiv conceded that Russian forces had made gains in the east, as Moscow's offensive saw it capture a number of villages in the Donbas region.

Russian forces were said to still be attacking the Azolstal steel plant in Mariupol, where fighters and some civilians are holed up.

Russian authorities said there were blasts early on Wednesday in three Russian provinces bordering Ukraine. An ammunition depot in the Belgorod province caught fire.

Concern increased over the prospect of the conflict widening to Ukraine's neighbor. Pro-Russian separatists there have blamed Ukraine for reported attacks in the Trans-Dniester region, which Ukraine says are "false-flag" incidents intended to escalate the war.

German Foreign Minister Annalena Baerbock defended Berlin's decision to supply heavy weapons to Ukraine.

The delivery of weapons — including heavy weapons such as tanks — is "the right step," Baerbock said.