Vladimir Putin has warned any countries attempting to interfere in Ukraine would be met with a “lightning-fast” response from Moscow. In an address to lawmakers in St Petersburg, the Russian president said troops would use “all the tools for this — ones that no one can brag about”.

The crisis in Ukraine must be the “catalyst for change” to overhaul the west’s approach to international security, the UK’s foreign secretary, Liz Truss, has said. Truss described Putin, as a “desperate rogue operator with no interest in international norms” and called upon the west to “dig deep” into its weapons inventories. “We’ve got to double down on our support for Ukraine,” she said.

The UK is “digging deep” into its inventories, including heavy weapons, tanks and aeroplanes, to defend Ukraine and other countries threatened by Russia, Truss added. “Some argue we shouldn’t provide heavy weapons for fear of provoking something worse. But my view, is that inaction would be the greatest provocation,” she said.

The United Nations secretary general, António Guterres, has arrived in Ukraine after meeting Putin and his foreign minister, Sergei Lavrov, in Moscow. Guterres will meet the Ukrainian president, Volodymyr Zelensky, on Thursday.

Russia has warned other EU customers may be cut off from Russian natural gas supplies if they refuse to pay in roubles. Kremlin spokesperson Dmitry Peskov’s comments came after Russia halted gas supplies to Poland and Bulgaria, a move that European leaders denounced as “blackmail”, which the Kremlin later denied. Poland’s prime minister, Mateusz Morawiecki, described Russia’s move as “a direct attack” on Poland.

The White House denounced Russia’s move to cut off energy supplies to Poland and Bulgaria. Press secretary Jen Psaki told reporters at a daily briefing on Wednesday: “Unfortunately this is the type of step, the type of almost weaponising energy supplies that we had predicted that Russia could take in this conflict.”

Volodymyr Zelenskiy described Russia’s actions as amounting to “energy blackmail” against Europe in his nightly national address. Zelenskiy said Russia’s decision to cut off gas supplies to Poland and Bulgaria shows “no one in Europe can hope to maintain any normal economic cooperation with Russia”.

A Ukrainian commander in the besieged city of Mariupol said there are more than 600 injured civilians and fighters in the Azovstal steel works. Serhiy Volyna, acting commander of the 36th marine brigade, said hundreds of civilians including children were living in unsanitary conditions and running out of food and water. Officials earlier said Russian forces were again attacking the huge steel plant.

The interior ministry of Moldova’s breakaway region of Transnistria issued a statement claiming it came under attack from Ukraine. It said drones were spotted and shots were fired near Kolbasna, which it claims contains one of the largest ammunition dumps in Europe.

A former head of the Polish army has accused Boris Johnson of “tempting evil” by revealing that Ukrainian soldiers were being trained in Poland in how to use British anti-aircraft missiles before returning with them to Ukraine. Gen Waldemar Skrzypczak complained that a loose-lipped PM had revealed too much to the Russians and that his remarks risked the safety of the soldiers involved.

The European Commission has proposed suspending import duties on all Ukrainian products to help the country’s economy during the war with Russia. The proposed one-year suspension, which would need to be approved by the European Parliament and its 27 member states, comes a day after Britain announced it was dropping all tariffs on Ukrainian goods.

Russia’s foreign ministry announced sanctions on 287 members of Britain’s House of Commons, accusing them of “whipping up Russophobic hysteria”. The UK prime minister, Boris Johnson, said those members who had been hit with sanctions by Russia should regard it as “a badge of honour”.

A top executive at one of Russia’s largest private banks said he has quit his post and fled to Kyiv to fight for Ukraine. In an interview with the independent Russian news outlet The Insider, Ukrainian-born Igor Volobuev, vice president of Gazprombank, said he “could no longer be in Russia” and that he wants to “wash off” his Russian past.

Two American volunteers fighting in Ukraine were reportedly wounded by artillery fire near the city of Orikhiv in the Zaporizhzhia region. US army veterans Manus McCaffrey and Paul Gray were working together as a team targeting Russian tanks with Javelin anti-tank systems when they were injured, according to reports.

The total losses inflicted upon Ukraine from the war have reached $600bn, Zelenskiy said. “More than 32m square metres of living space, more than 1,500 educational facilities and more than 350 medical facilities have been destroyed or damaged,” he added. “About 2,500km of roads and almost 300 bridges have been ruined or damaged.”