A Coastguard spokeswoman said they were hoping to get in contact with the parents of the two boys.
She said: "We would like to hear from the parents to confirm that the children are, in fact, safe."
It is understood that the boys were reported missing at midday but the parents had not been in contact with the emergency services since about 1pm.
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It will be increasingly humid and thundery with highs of 30C or more today.
Holidaymakers in Tunisia are determined not to be beaten. But, as Neil Connery writes, it won't be easy to escape the shock of the massacre.
Drink lots of water, stay out of the sun during the middle of the day, and take particular care of vulnerable people.