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We report here gamma-ray, X-ray and near-infrared observations of GRB040223along with gamma-ray and optical observations of GRB040624. GRB040223 wasdetected by INTEGRAL close to the Galactic plane and GRB040624 at high Galacticlatitude. Analyses of the prompt emission detected by the IBIS instrument onINTEGRAL are presented for both bursts. The two GRBs have long durations, slowpulses and are weak. The gamma-ray spectra of both bursts are best fit withsteep power-laws, implying they are X-ray rich. GRB040223 is among the weakestand longest of INTEGRAL GRBs. The X-ray afterglow of this burst was detected 10hours after the prompt event by XMM-Newton. The measured spectral propertiesare consistent with a column density much higher than that expected from theGalaxy, indicating strong intrinsic absorption. We carried out near-infraredobservations 17 hours after the burst with the NTT of ESO, which yielded upperlimits. Given the intrinsic absorption, we find that these limits arecompatible with a simple extrapolation of the X-ray afterglow properties. ForGRB040624, we carried out optical observations 13 hours after the burst withFORS 1 and 2 at the VLT, and DOLoRes at the TNG, again obtaining upper limits.We compare these limits with the magnitudes of a compilation of promptlyobserved counterparts of previous GRBs and show that they lie at the very faintend of the distribution. These two bursts are good examples of a population ofbursts with dark or faint afterglows that are being unveiled through theincreasing usage of large diameter telescopes engaged in comprehensiveobservational programmes.Comment: 13 pages, 12 figures, accepted for publication in A&

The weakINTEGRALbursts GRB 040223 and GRB 040624: an emerging population of dark afterglows