TOKYO, Feb 18 - Japanese stocks ended lower on Wednesday amid uncertainty about where the yen would head after robust economic growth data, although firms with positive news like NTT DoCoMo Inc <9437.T> and Yahoo Japan <4689.T> gained. Japan's economy grew at its fastest clip in over 13 years, with gross domestic product (GDP) surging by an annualised 7.0 percent in October-December to beat a median forecast of 4.6 percent, data released just before the opening showed. But with traders suspicious that the Bank of Japan had intervened in the currency market, the yen failed to move strongly in either direction on the GDP data, in turn putting a lid on active stock trade. After a small jump at the open, the Nikkei average <.N225> lost steam in the afternoon and closed down 0.23 percent at 10,676.81. That followed a 1.44 percent rise in the previous session, which was the largest percentage gain in a month. The broader TOPIX index <.TOPX> also closed lower, down 0.15 percent at 1,052.98.//www..com