  We present HST/NICMOS observations (1.1-2.2micron) and 1.9-4.1micron
spectroscopy of the central region of the dwarf galaxy NGC5253. The HST/NICMOS
observations reveal the presence of a nuclear double star cluster separated by
0.3-0.4arcsec or 6-8pc (for a distance d=4.1Mpc). The double star cluster, also
a bright double source of Pa-alpha emission, appears to be coincident with the
double radio nebula detected at 1.3cm. The eastern near-infrared star cluster
(C1) is identified with the youngest optical cluster, whereas the western star
cluster (C2), although it is almost completely obscured in the optical, becomes
the brightest star cluster in the central region of NGC 5253 at wavelengths
longer than 2micron. Both clusters are extremely young with ages of
approximately 3.5 million years old. C2 is more massive than C1 by a factor of
6 to 20 (M(C2)= 7.7 x 10^5 - 2.6 x 10^6Msun, for a Salpeter IMF in the mass
range 0.1-100Msun). Analysis of the circumnuclear spectrum excluding C1 and C2,
as well as of a number of other near-infrared selected clusters with a range of
(young) ages, suggests that the star formation was triggered across the central
regions of the galaxy. We have also modelled the nuclear UV to mid-infrared
spectral energy distribution (SED) of NGC5253 and found that the infrared part
is well modelled with a highly obscured (A_V= 17mag) young starburst with a
stellar mass consistent with our photometric estimates for C1 and C2. The SED
model predicts a moderately bright polycyclic aromatic hydrocarbon (PAH)
feature at 3.3micron that is not detected in our nuclear L-band spectrum.
NGC5253's low metallicity and a top-heavy IMF likely combine to suppress the
3.3micron PAH emission that is commonly seen in more massive starburst systems.
