Commentary
The Holy Qur'an does describe this state of the people Dhul-Qarnain found living towards the East meaning thereby that they were not accustomed to the use of ways and means like houses, tents and dresses to seek protection against the Sun. But, it does not mention anything about their faith and deeds, nor does it say what Dhul-Qarnain did to them.
However, it is obvious that these people too were infidels and Dhul-Qarnain handled them the way he had handled the people he had found in the West as mentioned earlier. But, describing it again at this place was not considered necessary since finding it out is also possible on the analogy of the previous event. (As in al-Bahr al-Muhit from Ibn Atiyyah)