* Fall in U.S. futures adds to concern - analysts
* Insurance sector underperforms on profit-taking
By Ayai Tomisawa
TOKYO, March 6 (Reuters) - Japanese shares fell on Monday as the yen firmed and as global geopolitical tensions rose after North Korea fired four missiles, three of which landed in Japan's exclusive economic zone.
The Nikkei share average fell 0.5 percent to 19,385.71 points by mid-morning.
The dollar fell against the yen on Monday as investors locked in gains after the greenback's rise last week on growing expectations of a U.S. interest rate hike this month.
The dollar slipped 0.2 percent to 113.83 yen, down from Friday's high of 114.75.
"On top of the stronger yen, a fall in U.S. futures is also stoking concerns that U.S. shares will fall later in the day," said Yutaka Miura, a senior technical analyst at Mizuho Securities.
Sentiment deteriorated further after North Korea fired the ballistic missiles early on Monday, he added.
U.S. stock index futures fell after the North Korean launch and on growing domestic political tensions after President Donald Trump accused his predecessor, Barack Obama, of wiretapping him.
Defense-related stocks outperformed on speculation that North Korea's latest launch will spur more spending on arms.
Land mine maker Ishikawa Seisakusho jumped 6.1 percent, while Mitsubishi Heavy Industries rose 0.5 percent and Kawasaki Heavy Industries gained 0.9 percent.
The insurance sector, which rose recently, lost ground and was down 1.6 percent to become the worst performer on the board. Dai-ichi Life Holdings dropped 1.6 percent and MS&AD Insurance fell 1.8 percent.
Sumitomo Mitsui Financial Group Inc declined 2.5 percent after the bank said it would sell 37.2 million of its own shares in a secondary offering.
The broader Topix shed 0.3 percent to 1,553.77 and the JPX-Nikkei Index 400 declined 0.3 percent to 13,907.63.
Editing by Kim Coghill