Delivering heavier weaponry to Ukraine such as tanks, would not, according to Germany's justice minister, constitute an entry into the war against Russia.

German politics has been consumed since the start of the conflict at the end of February by the question of what kind of weaponry to give Ukraine, and how fast to deliver it.

Pressure has come directly from Kyiv, where leaders are urging Germany to deliver more weapons to help fight off Russian troops.

Social Democrat Chancellor Olaf Scholz has refused to commit to sending heavier weapons such as tanks, helicopters and planes, although the voices from within his center-left coalition pushing for stronger military support are getting louder.

Justice Minister Marco Buschmann from the liberal Free Democrats, the smallest party in the coalition, told the Welt am Sonntag newspaper that international law does not categorize weapons deliveries as an entry into war.

"So if (Ukraine) exercises its legitimate right of self-defense, supporting it by supplying weapons cannot lead to becoming a party to the war," he said in remarks seen by Deutsche Presse-Agentur (dpa) on Saturday.

He said this was not only his personal view but that of the German government.

Buschmann said Germany was among the first countries to start systematically investigating possible war crimes in Ukraine, involving federal police and the attorney general.

Russian President Vladimir Putin, however, would be exempt in any case, Buschmann said. International law stipulates that active heads of state may not be investigated.

"There is no doubt that disgusting and horrible atrocities are being committed in Ukraine by Russian soldiers," he said.

To legally prove genocide – as has been claimed by U.S. President Joe Biden, among others – there would have to have been an intent to destroy, in whole or in part, a national, racial, religious or ethnic group, Buschmann explained.

He could not yet say whether there was evidence of this.