Six weeks into the invasion -- Western nations are stepping up military support for Ukraine as Russian forces concentrate their attacks on the country's east.

Russia's defense ministry said on Wednesday its missile strikes had destroyed Ukrainian infrastructure that supplied fuel to troops in Kharkiv and Mykolaiv.

Britain's defense ministry reports heavy fighting and Russian airstrikes continue in the strategic port city of Mariupol. It says the humanitarian situation in the city is worsening. It adds Russian forces are apparently trying to force a surrender by preventing aid from reaching the 160,000 residents still trapped there.

Russian troops are being accused of torturing, raping and murdering civilians in areas they once controlled.

Kyiv Mayor Vitali Klitschko said, "The Russians, what they did in Bucha is genocide of Ukrainian population. They killed all people."

Reuters has reported many bodies were found on Tuesday in the town of Borodyanka, near Bucha. It's believed they were noncombatants.

The news agency says police have not finished counting the number of the dead.

A local resident said, "I don't know exactly what happened to that building, but there are people under the debris. I think a tragedy happened over there."

Another resident said, "This was a child's room. The Russians went through everything they could find. They even took the child's phone."

Ukraine's top prosecutor said there were more victims in Borodyanka than anywhere else in the Kyiv region.

Western nations are imposing fresh sanctions in a bid to compel a Russian withdrawal.

The US government has blocked Moscow from paying down its debt with dollars held in American banks. Market analysts say the move will raise the risk of default.

The European Union says it will ban coal imports from Russia -- a crucial source of revenue for the country.

Foreign chiefs from NATO are scheduled to meet on Wednesday and Thursday. G7 foreign ministers will also hold talks this week.

The US Secretary of State Antony Blinken says those meetings will support the effort to hold Russia accountable.

NATO Secretary General Jens Stoltenberg told NHK the Czech Republic will provide tanks to Ukraine. The details aren't clear but local media report the country will send dozens of combat vehicles, including Soviet-era tanks.

Stoltenberg said, "Supported by equipment from NATO allied countries has enabled them to really put up to a real fight, to resist the invading Russian troops. NATO allies will discuss at the foreign ministerial meeting, what more we can do."

Meanwhile, a Chinese foreign ministry spokesperson on Wednesday called for a thorough investigation into the alleged killings of civilians in Bucha.

He said each country should avoid making unfounded accusations until the facts are known.