We present a detailed study of the X-ray energy and power spectral properties of the neutron star transient IGRJ17191-2821. We discovered four instances of pairs of simultaneous kilohertz quasi-periodic oscillations (kHz QPOs). The frequency difference between these kHz QPOs is between 315 and 362Hz. We also report on the detection of five thermonuclear type I X-ray bursts and the discovery of burst oscillations at ~294Hz during three of them. Finally, we report on a faint and short outburst precursor, which occurred about two months before the main outburst. Our results on the broad-band spectral and variability properties allow us to firmly establish the atoll source nature of IGRJ17191-2821.