KIEV claimed today that it had seized the key town of Avdiivka near the Ukrainian rebel stronghold of Donetsk.

Meanwhile, heavy fighting around Donetsk prevented international experts from reaching the crash site of flight MH17 for a third time.

Almost two weeks after the Malaysia Airlines jet came down, international monitors from the Organisation for Security and Co-operation in Europe were turned back to Donetsk after being stopped a separatist checkpoint due to heavy fighting.

Regional officials in Donetsk said yesterday that 19 people had been killed in fighting over the past 24 hours. 

Several apartment buildings have been hit by shelling in the government forces’ continuing bid to retake the city.

Ukraine says its troops have also entered the towns of Shakhtarsk and Torez in Donetsk region and Lutuhyne in Lugansk region.

In Moscow, the Central Bank of the Russian Federation promised it would support Russian financial institutions hit by US or European Union sanctions over the country’s alleged role in Ukraine.

The bank promised to “take adequate measures” to support targeted institutions. 

Shares in Russia’s state-owned VTB bank — which had been specifically named in sanctions proposals — dropped 1.2 per cent yesterday.

US officials had bragged on Tuesday that roughly 30 per cent of Russia’s banking sector assets were now constrained by sanctions.

The West has also halted future any forays into Russian markets, with the US announcing plans to block future technology sales to the oil industry and Europe approving an arms embargo. 

Europe also backed sanctions against state-owned banks and the energy sector.

Officials insist the new sanctions will damage the Russian economy. 

The International Monetary Fund has slashed Russia’s growth forecast for this year to nearly zero, down from 1.3 per cent last year and the US claims more than £59 billion in capital will flow out of the country.

But it remained uncertain whether tougher penalties would have any impact on Russian actions in Ukraine — nor was it clear what further actions the US and Europe were willing to take if the situation remained unchanged.