When the Ukrainians refused, citing the 2003 Russo-Ukrainian treaty on freedom of navigation in the relevant area, the Russian boats attempted to intercept them, and rammed the tugboat Yany Kapu several times.[9][45] When they tried to ram the more agile gunboats, two Russian ships collided, and the Russian Coast Guard Rubin-class patrol boat Izumrud was damaged.[46] The Ukrainian naval vessels then continued their journey, stopping near the anchorage 471 waiting zone, about 14 kilometres (9 mi) from the Crimean Bridge, and remained there for the next eight hours.[5] During this time, the Russians placed a large cargo ship under the bridge, blocking the route into the Sea of Azov.[6][24][9][47] Concurrently, Russia scrambled two fighter jets and two helicopters to patrol the strait.[9] In the evening, the Ukrainian ships turned back to return to port in Odessa.