MSCI's broadest index of Asia-Pacific shares outside Japan fell 0.5 percent, as markets remained unconvinced that a European Union summit on Thursday and Friday this week will make any substantial progress towards resolving the debt situation.

As this week marks the end of the April-June period, some investors are expected to sell to book gains, market participants said.

The Treasury Department will also be offering $35 billion in two-year notes on Tuesday, $35 billion in five-year notes on Wednesday and $29 billion in seven-year notes on Thursday.

"There is some supply coming in this week at a time when some people are going to be looking to sell, not buy, but as long as Europe keeps the 'risk-off' trade alive, then they will find buyers, as they did today," said a fixed-income fund manager at a Japanese asset management firm.

The yield on US 10-year notes fell to 1.65 percent from 1.67 percent in late US trade, but remained above 1.62 percent in Tokyo on Friday.

The yields on 30-year bonds stood at 2.74 percent, down slightly from 2.75 percent in late US trade but above 2.69 percent in Tokyo trade on Friday.

On Friday, the Federal Reserve purchased $1.83 billion in bonds due 2036 to 2042 as part of its "Operation Twist" stimulus programme, under which it sells short-term notes and buys longer-term debt with he aim of pushing down long-term rates.