A delegation headed by Greek minister for protection of citizens Michalis Chrysohoidis, on an official visit to Bulgaria, has signed a treaty on bilateral co-operation with his Bulgarian counterpart, Interior Minister Tsvetan Tsvetanov, Focus news agency said.Reportedly, Tsvetanov was delighted at the outcome of the meeting with his Greek colleague."We spoke of increasing bilateral co-operation, and the goals that we want to achieve; the means and organisation with which we want to combat organised crime," Tsvetanov said. According to the Bulgarian Minister, it was essential that Greece and Bulgaria act assertively because in times of economic crisis, criminal activity rises proportionately, including trans-border crime."Any economic crisis is a feeding ground for organised crime rings," Tsvetanov said. High on the agenda of the discussion were human trafficking, drugs distribution and skimming equipment.Tsvetanov said that the two countries could only benefit from the exchange of information and from stronger co-operation. He also expressed his gratitude to Greece for always backing Bulgaria regarding the Schengen agreement."It was an honour for me to accept the invitation from Mr Tsvetanov and come to Sofia. It is also an honour and a pleasure for me to work with an interior minister like Tsvetanov," Chrysohoidis was quoted as saying by Focus news agency.