* Nikkei adds 2.5 pct weekly gains
* Both volume and turnover highest in nearly a month
* Financials, exporters in demand
By Ayai Tomisawa
TOKYO, June 2 (Reuters) - Japan's Nikkei share average broke through the 20,000-point level for the first time since December 2015 on Friday as strong U.S. economic data and a weaker yen boosted investor confidence.
The Nikkei climbed 1.6 percent to 20,177.28 points, its highest close since mid-August 2015. For the week, it gained 2.5 percent.
Both trading volume and turnover were heavy, with 2.3 billion shares changing hands on the main board with a trading value of 3.2 trillion yen, both the highest level since May 8.
The broader Topix advanced 1.6 percent to 1,612.20.
The threshold of "20,000 is a big technical and psychological level for traders, so we should be not be surprised if we see some resistance at this level," said Gavin Parry, managing director at Parry International Trading Ltd.
Traders added that when there is a recovery seen in the global environment, there is a greater focus on Japan Inc. earnings, which saw profit growth of 16 percent in the fiscal year through March.
"Japanese stocks would have risen to this level earlier if we did not see global risks and the rising yen," said Norihiro Fujito, a senior investment strategist at Mitsubishi UFJ Morgan Stanley Securities.
But U.S. political turmoil could unnerve investors next week again, Fujito said.
Former FBI Director James Comey will testify next Thursday before a U.S. Senate panel investigating Russia's alleged meddling in the 2016 U.S. election, in a hearing that could add to difficulties facing President Donald Trump.
"The market is worried that the allegations against Trump over his interference with a federal investigation would delay his efforts on tax cuts and economic policy," Fujito said, adding that there is also a risk that the dollar will fall against the yen, hurting Japanese stocks.
This week's gains have also pushed the Nikkei into overbought territory on a technical basis, with its Relative Strength Index (RSI) at 77, leaving it vulnerable to profit taking.
Cyclical sectors were pushed up by recovering risk appetite, with financials and exporters outperforming.
Nomura Holdings jumped 5.3 percent, Mitsubishi UFJ Financial Group soared 4.4 percent, while insurer T&D Holdings surged 4.1 percent. Subaru Corp added 3.9 percent and Kyocera Corp advanced 3.3 percent.
Editing by Simon Cameron-Moore and Kim Coghill