President Abdullah Gul of Turkey accused the European Union on Friday of “interfering” by asking Ankara to withdraw an invitation for Omar Hassan al-Bashir, Sudan’s indicted president, to attend an Islamic summit in Istanbul.

The row threatens to stir fresh tensions between Turkey and its western allies after a month in which Turkish leaders have forged new trade links with Iran and Syria and provoked a crisis in relations with Israel by ejecting it from joint military exercises.