Russia’s Constitutional Court has approved the accession treaties signed by President Vladimir Putin allowing four former Ukrainian regions to become part of the Russian Federation after referendums.

Moscow has announced a partial mobilization of Russian forces, calling reservists into active service as the country faces a protracted conflict in the Ukraine and Donbas.

Josep Borrell said the political decision was made to apply new sectorial and individual measures against Moscow.

One of Russia's most senior security officials says he favors holding referendums in the breakaway Donbass region of eastern Ukraine in order to formally make them part of Russia.

Russia says its forces were carrying out "massive strikes" on Ukrainian armed forces from all operational directions across the Ukrainian front line, as Kiev said it was prepared to liberate all of its territory while calling on the West to speed up the deliveries of weapons systems to the county.

Nearly six months into the war between Russia and Ukraine, fierce fighting is reported in Ukraine's Donetsk as Russian forces further press on with plans to seize the entire eastern region of the Donbass.

Russian forces are pressing ahead with their months-long military offensive to capture eastern Ukraine, with the former Soviet country calling for a Western-led ban on all Russians amid heavy fighting between the two sides.

Ukraine has boosted its drive to retake Russian-controlled south with the help of airstrikes.

As Russia continues its advance in the eastern Ukrainian region of Donbas, Johnny Miller has traveled to a city which has seen some of the fiercest fighting of the war so far.

The Western-supplied weapons include long-range arms which Kiev says are beginning to help on the battlefield.