Asked whether the frigate Baden-Wuerttemberg and the supply ship Frankfurt am Main were headed into or through the Strait, Defence Minister Boris Pistorius said "I can confirm that".

"And the message is a very simple one, which we have always supported... international waters are international waters," Pistorius told journalists.

US and other military ships have often sailed through the sensitive waterway but it was the first time in over two decades that the German navy has done so, German media reports said.

Taiwan's defence ministry in a brief statement said that "a German frigate and a supply ship sailed through the Taiwan Strait from north to south since this morning".

"The military has monitored the situation and no anomaly was detected in our surroundings."

Beijing views Taiwan as a renegade province and claims jurisdiction over the body of water that separates the island from the Chinese mainland.

Germany and many other countries argue such voyages are usual, citing freedom of navigation in international waters.

The two German vessels were headed from South Korea to the Philippines, defence ministry officials said.

Pistorius said that the course charted by the vessels was "the shortest route".

"It is the safest route given the weather conditions. And these are international waters, so we are sailing through them."

Global tracking service MarineTraffic on Friday showed the vessels sailing into the Strait, on a southerly course at a location to the west of Taipei.

German magazine Der Spiegel had first reported the planned voyage last week, but German defence officials did not immediately confirm the plans.

Taiwan's foreign ministry said on Tuesday it "welcomes and affirms Germany, along with the US, Canada and the Netherlands, for taking actions to demonstrate the legal status of the Taiwan Strait as international waters, while defending freedom of navigation and maintaining regional peace at the same time".

A business group in Europe's largest economy, the Federation of German Industries, welcomed the move.

"German industry is encouraging the federal government to maintain the already eroding rules-based international order as far as possible," executive board member Wolfgang Niedermark told the Handelsblatt financial daily.

He said rules are only valid if they are enforced consistently, and that "Germany too must take responsibility for this".