Sporadic cometary-like activity has been observed in three asteroids of the main belt (the Main Belt Comets, MBCs, Hsieh and Jewitt 2006, Science, 312, 561): (7968) Elst-Pizarro, 118401 (1999 RE70) and P/2005 U1 (Read). All of them are members of the Themis family. The study of this objects is of fundamental importance to address several astronomical problems like end states of comet nuclei, and abundance of water in main belt asteroids and its role as a possible source of terrestial water. We present CCD spectroscopic and photometric observations of the three MBCs, compare them with other activated asteroids of the NEO population, other Themis family asteroids, comet nuclei and asteroids in cometary orbits. On images of Elst-Pizarro obtained during May, June and Jully using the 4.2m William Herschel (WHT), the 3.56m Telescopio Nazionale Galileo (TNG) and 2.5 Nordic Optical Telescope (NOT) of "El Roque de los Muchachos Observatory” the object presents a straight tail similar to that observed during its previous perihelion passages. 118401 was intensively observed with the NOT telescope from Jan. 19 to 22, 2007, and no signs of activity were observed. The lightcurve is indicative of a rotation period > 22hr. Also P/2005 U1 (Read) present a point-like FWHM. Spectra of Elst-Pizarro in the 0.38-0.9 microns range obtained with the WHT and TNG on June 19 and July 9 are typical of C- or B-type asteroids, with spectral slopes S'=-0.5 and 1%/0.1microns respectively. Also an absorption band below 0.5 microns is observed, very similar to the spectrum of other Themis family asteroids. A spectrum of 118401 in the 0.4-0.7microns range obtained with the NOT telescope is typical of B-type asteroid (S'=-1%/0.1 microns). We will also present images and spectra obtained with the VLT late July . We finally discuss the cometary or asteroidal nature of the MBCs.