We report results of a multi-band monitoring campaign of the flat spectrum radio quasar TXS 0536 + 145 at redshift 2.69 .
This source was detected during a very high \gamma -ray activity state in 2012 March by the Large Area Telescope on board Fermi , becoming the \gamma -ray flaring blazar at the highest redshift 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 ^ { -1 } which is comparable to the values achieved by the most luminous blazars .
This activity triggered radio-to-X-rays monitoring observations by Swift , Very Long Baseline Array , European VLBI Network , and Medicina single-dish telescope .
Significant variability was observed from radio to X-rays supporting the identification of the \gamma -ray source with TXS 0536 + 145 .
Both the radio and \gamma -ray light curves show a similar behaviour , with the \gamma -rays leading the radio variability with a time lag of about 4-6 months .
The luminosity increase is associated with a flattening of the radio spectrum .
No new superluminal component associated with the flare was detected in high resolution parsec-scale radio images .
During the flare the \gamma -ray spectrum seems to deviate from a power law , showing a curvature that was not present during the average activity state .
The \gamma -ray properties of TXS 0536 + 145 are consistent with those shown by the high-redshift \gamma -ray blazar population .