Turkey has barred a German delegation from visiting an air base used to fight jihadists in Syria, amid a bitter diplomatic spat between Berlin and Ankara, officials said Wednesday.

Germany's parliament early this month infuriated Turkish President Recep Tayyip Erdogan by declaring the Ottomans' First World War-era massacre of Armenians a genocide, sparking threats of retaliation by the NATO partner country.

Ankara has now cancelled a previously-scheduled July visit by Germany's state secretary for defence Ralf Brauksiepe and other lawmakers to Incirlik air base, a German defence ministry spokesman said.

"The Turkish authorities at the moment are not approving the travel plans," said the spokesman.

"There is no written statement on the reason," he said, adding that the delegation still hoped to make the trip.

News website Spiegel Online reported a ministry official had told a closed parliamentary panel that Turkey had said it blocked the visit because of the Armenia vote.

Germany last December agreed to send Tornado surveillance jets and tanker aircraft to Incirlik to aid the multinational coalition fighting the Islamic State group in neighbouring Syria.

Since then German-Turkish relations have come under increasing strain, with Germany criticising Turkey's tough line against critical journalists and its Kurdish minority.

Ties plunged to a new low after the Armenia vote, when Erdogan charged that the 11 German MPs with Turkish roots who backed the resolution should undergo "blood tests" to see "what kind of Turks they are".

Source: AFP