The Nikkei index closed at a nearly two-week low Monday as uncertainty prevailed after Italian voters rejected proposed constitutional reform in a referendum, prompting Prime Minister Matteo Renzi to announce his resignation. 
The 225-issue Nikkei Stock Average ended down 151.09 points, or 0.82%, from Friday at 18,274.99. 
The broader Topix index of all First Section issues on the Tokyo Stock Exchange finished 11.02 points, or 0.75 %, lower at 1,466.96. 
Decliners were led by bank, service and real estate issues.