Tokyo's benchmark stock index dropped 1.65 percent at the start on Monday, one of the first major markets to open after Greeks voted to reject austerity measures demanded by the cash-strapped nation's creditors.

The Nikkei 225 at the Tokyo Stock Exchange fell 339.64 points to 20,200.15 in the first few minutes of trading, as investors digested the news which boosts the chances of Greece tumbling out of the eurozone.