High redshift blazars are among the most powerful objects in the Universe .
Although they represent a significant fraction of the extragalactic hard X-ray sky , they are not commonly detected in \gamma -rays .
High redshift ( z > 2 ) objects represent < 10 % of the AGN population observed by Fermi so far , and \gamma -ray flaring activity from these sources is even more uncommon .
The characterization of the radio-to- \gamma -ray properties of high redshift blazars represent a powerful tool for the study of both the energetics of such extreme objects and the Extragalactic Background Light .
We present results of a multi-band campaign on TXS 0536+145 , which is the highest redshift flaring \gamma -ray blazar detected so far .
At the peak of the flare the source reached an apparent isotropic \gamma -ray luminosity of 6.6 \times 10 ^ { 49 } erg/s , which is comparable with the luminosity observed from the most powerful blazars .
The physical properties derived from the multi-wavelength observations are then compared with those shown by the high redshift population .
In addition preliminary results from the high redshift flaring blazar PKS 2149-306 will be discussed .