Ukraine and Russia: What you need to know right now

* Moldova's president said a series of attacks in the Russia-backed breakaway region of Transdniestria were an attempt by factions within the territory bordering on Ukraine to stoke tensions, and the Kremlin voiced serious concern. DIPLOMACY, SANCTIONS, AID * United Nations Secretary-General Antonio Guterres told Russia's foreign minister on Tuesday he was ready to fully mobilise U.N. resources to save lives and evacuate people from the besieged Ukrainian city of Mariupol.

Washington and its allies met at a German air base on Tuesday to pledge new packages of ever heavier weapons for Ukraine, brushing off a threat by Moscow that their support for Kyiv could lead to nuclear war. SPILLOVER INTO MOLDOVA? * Moldova's president said a series of attacks in the Russia-backed breakaway region of Transdniestria were an attempt by factions within the territory bordering on Ukraine to stoke tensions, and the Kremlin voiced serious concern.

DIPLOMACY, SANCTIONS, AID * United Nations Secretary-General Antonio Guterres told Russia's foreign minister on Tuesday he was ready to fully mobilise U.N. resources to save lives and evacuate people from the besieged Ukrainian city of Mariupol. * Germany announced on Tuesday its first delivery of heavy weapons - Gepard anti-aircraft tanks - to Ukraine to help it fend off Russian attacks after weeks of pressure at home and abroad to do so amid confusion over its stance. FIGHTING

Reports of battlefield developments below could not be immediately verified by Reuters: * Ukraine's general staff said on Tuesday Russia's offensive continued in the eastern Kharkiv region with Moscow's forces trying to advance towards a village called Zavody. * Russia is probably trying to encircle heavily fortified Ukrainian positions in the country's east, the British military said in an update on Tuesday, noting forces were trying to advance towards the cities of Sloviansk and Kramatorsk. * Russia's defence ministry said its missiles destroyed six facilities powering railways used to deliver foreign weapons to Ukrainian forces in the eastern Donbas region. RUSSIAN WARNING * The powerful secretary of Russia's Security Council said on Tuesday that Western and Ukrainian government policy was leading towards the break-up of Ukraine.

QUOTES * "NATO, in essence, is engaged in a war with Russia through a proxy and is arming that proxy. War means war." - Russian Foreign Minister Sergei Lavrov. * "Nations from around the world stand united in our resolve to support Ukraine in its fight against Russia's imperial aggression - U.S. Defense Secretary Lloyd Austin. (Editing by Angus MacSwan and Mark Heinrich)