  Context: The discovery of new massive star clusters and massive stellar
populations in previously known clusters in our Galaxy by means of infrared
studies has changed our view of the Milky Way from an inactive to an active
star-forming machine. Within this scenario, we present a near-infrared
spectrophotometric study of the stellar content of the compact H II region
Sh2-152.
  Aims: We aim to determine the distance, extinction, age, and mass of Sh2-152,
using for the first time near-infrared stellar classification for several
sources in the region.
  Methods: Using our near-infrared (J, H, and Ks) photometry and the
colour-magnitude diagram for the cluster field, we selected 13 bright stars,
candidate members of the reddened cluster's main sequence, for H- and K-
spectroscopy and spectral classification. This near-infrared information was
complemented with an optical spectrum of the ionizing central star to confirm
its spectral nature.
  Results: From the 13 spectroscopically observed stars, 5 were classified as
B-type, 3 as G-type, 2 were young stellar objects (YSOs), and 3 remained
unclassified (because of the poor data quality). The cluster's extinction
varies from A_{Ks}=0.5 to 2.6 magnitudes (A_V=4.5 to 24 magnitudes) and the
distance is estimated to be 3.21\pm0.21 kpc. The age of the cluster is younger
than 9.4 Myr and the lower limit to the total mass of the cluster is
(2.45\pm0.79)\cdot10^3 M_{Sun}. We compare the number of ionizing photons
emitted from the OB-type stars with the Lyman continuum photons derived from
the radio observations and conclude that both quantities are consistent for the
central region of Sh2-152. In contrast, the main ionizing source of the lower
region remains unidentified.
