ISTANBUL (Reuters) - A Islamic State suicide bomber who killed 10 German tourists in Istanbul entered Turkey as a refugee and his movements were not monitored as he was not on any watch lists, Turkish Prime Minister Ahmet Davutoglu said on Wednesday.

Asked whether Turkey planned air strikes against Islamic State in response to the bombing, Davutoglu said Turkey would act at a time and in a manner that it saw fit.

He said Russia’s entry into the Syrian civil war had become a barrier to Turkish air strikes against Islamic State, and that the Russian air force appeared to be protecting the radical Sunni militants.