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We carried out photometric and low-resolution spectral observations of sixeclipsing ultrashort-period binaries with MS components. The light curvesolutions of the Rozhen observations show that all targets are overcontactsystems. We found well-defined empirical relation "period -- semi-major axis"for the short-period binaries and used it for estimation of the globalparameters of the targets. Our results revealed that NSVS 925605 is quiteinteresting target: (a) it is one of a few contact binaries with M components;(b) it exhibits high activity (emission in H$\alpha$ line, X-ray emission,large cool spots, non-Planck energy distribution); (c) its components differ intemperature by 700 K. All appearances of high magnetic activity and hugefillout factor (0.7) of NSVS 925605 might be assumed as a precursor of thepredicted merging of close magnetic binaries. Another unusual binary is NSVS2700153 which reveals considerable long-term variability.

Ultrashort-period MS eclipsing systems. New observations and light curve solutions of six NSVS binaries