A system for generating cold plasma is presented, suitable for use in in-vivo treatment of biological tissue. The system comprising: a control unit connectable to an elongated member at a first proximal end of the elongated member. The elongated member comprises a plasma generating unit at a second distal end thereof and gas and electricity transmission channels extending from said first proximal end towards said plasma generating unit. The control unit comprises a gas supply unit configured to provide predetermined flow rate of selected gas composition through said gas transmission channel and a power supply unit configured to generate selected sequence of high-frequency electrical pulses, typically in mega Hertz range, directed through said electricity transmission channel, thereby providing power and gas of said selected composition to the plasma generating unit for generating cold plasma.