sentences:  The reason for those ground works was to stop Russian ships from having to pay a toll to Ukraine for crossing the strait of Kerch, which is considered as territorial waters of Ukraine.Ukraine refused to recognize the strait as inner waters of both countries until 2003.On October 21, 2003 the Border Service of Ukraine arrested the Russian tugboat "Truzhenik" that crossed the State Border of Ukraine and conducted photo and video surveillance of the island.