Japan's core consumer prices dipped 0.1 percent in May from a year earlier, declining for a fourth straight month and at the same pace as in April, the government said.

The core consumer price index (CPI) for Tokyo alone in June -- seen as a leading indicator for national price trends -- was also down 0.1 percent, dampening hopes of a near-term pick-up in the country-wide indicator.

"I think CPI will remain negative into June. The price pressures remain fairly limited right now," said Hiromichi Shirakawa, chief economist for Japan at Credit Suisse.

Renewed concerns over deflation have created a headache for the central bank, which last July raised interest rates for the first time in almost six years, followed by another quarter-point hike to 0.5 percent in February.

But Mamoru Yamazaki, chief economist for Japan at RBS Securities, said if next week's Tankan or central bank survey of business confidence shows firms are upgrading their capital spending plans, then the BoJ could hike rates in August.

"There is no clear sign of sustained positive growth in the CPI," said Yamazaki.