We report NIR broad and narrow band photometric observations in the direction of the IRAS17149-3916 source that reveal the presence of a young cluster of massive stars embedded in an HII region coincident with RCW121 .
These observations , together with published radio data , MSX and Spitzer images were used to determine some of the physical parameters of the region .
We found 96 cluster member candidates in an area of about 1.5 \times 2.0 square arcmin , 30 % of them showing excess emission in the NIR .
IRS 1 , the strongest source in the cluster with an estimated spectral type of O5V-O6V ZAMS based on the color-magnitude diagram , is probably the main ionizing source of the HII region detected at radio wavelengths .
Using the integrated Br \gamma and the 5 GHz flux densities , we derived a mean visual extinction A _ { V } = 5.49 \pm ^ { 2.06 } _ { 1.32 } magnitudes .
From the observed size of the Br \gamma extended emission , we calculated the emission measure E = 4.5 \times 10 ^ { 24 } cm ^ { -5 } and the electron density n _ { e } = 2.6 \times 10 ^ { 3 } cm ^ { -3 } , characteristic of compact HII regions .