A "death cross" has formed over Japanese real estate investment trusts (REITs) for the first time in Shinzo Abe's 30-month prime ministership, fueling speculation a bear market is imminent and equities are about to get hit.

The Tokyo Stock Exchange's REIT index plunged to an eight-month low last week, causing its 20-day moving average to fall below the 200-day moving average and creating the so-called death cross on technical charts. Large sell orders, most likely from Japanese investors, were the main culprit behind the fall, a trader said.

The REIT index has lost as much as 10 percent this month, and has surrendered all its gains since the central bank surprised markets with additional stimulus in late October. The stimulus included a tripling of the Bank of Japan's purchases of REITs.

The REIT decline suggests an increasingly cautious outlook for Japan's property market, where real estate values have risen but rents have not. That spells potential trouble for Abe's economic policies, which aim to reflate the world's third-biggest economy through asset price appreciation.

"When REITs fall, stocks often tend to follow them. So it is not a good sign for stocks as well," said Hiroshi Ono, manager of equity investment at Sumitomo Insurance. Indeed, in 2007, the REIT index peaked out two months before a separate high in the Nikkei 225 share average. In 2013, a peak in REITs arrived about two months before a mini-collapse in the broader equities market in May.