Taiwan took the unprecedented step on Monday of sending coast guard vessels into waters claimed by Japan, highlighting the much tougher stance the island’s new government is taking on the neighbour it had so far viewed as its closest unofficial ally in Asia.

Ten patrol boats accompanied a fishing vessel to just one sea mile off the Diaoyutais, or Senkakus, islands controlled by Japan but also claimed by Taiwan and China, according to the coast guard in the port of Shenao, to which the group safely returned on Monday.