Berlin (dpa) – The already tense relationship between Berlin and Kiev appeared to further deteriorate on Sunday, as comments made by a veteran German politician led to a public exchange of grievances on Twitter.

The relationship between the two allies has been tense for weeks given what the Ukrainian government sees as the ruling Social Democrats’ historic close ties to the Kremlin, as well as the current German government’s reluctance to supply heavy weaponry to Ukraine.

The Ukrainian government even went as far as snubbing German President Frank-Walter Steinmeier over a trip the German head of state wanted to make to Kiev earlier this month, citing Steinmeier’s record on supporting closer ties with Russia during his time as foreign minister.

Former German foreign minister Sigmar Gabriel defended Steinmeier’s record in an guest column for the Spiegel magazine published on Sunday, and hit back at Kiev, saying that the Ukrainian government had been making “targeted” attacks on the German head of state, and accusing Ukraine’s ambassador to Berlin, Andriy Melnyk, of spreading “conspiracy theories.”

Melnyk, already well known in Germany for his outspokenness over Berlin’s apparent prevarication regarding heavy weapons deliveries to Kiev, reacted swiftly and sharply on Sunday, saying that it was Gabriel and his “SPD cronies’ years of Putin-friendly policy that has brought about the barbaric war of extermination.”

Melnyk also accused Gabriel of concealing his “personal political responsibility for Putin’s Nord Stream 2 project,” which he launched as German vice-chancellor in 2015.