* USD/JPY drops below 111, escalating worries about earnings

* Oil shares dip after crude prices fall

* Shareholder returns exceeded 5 trln yen last FY - Nomura

* Fast Retailing contributes hefty negative points to Nikkei

By Ayai Tomisawa

TOKYO, April 5 (Reuters) - Japan's Nikkei share average tumbled to a six-week low on Tuesday morning after the stronger yen hurt the overall market mood, while a drop in Fast Retailing Co weighed after the clothing company reported a poor monthly sales.

Investors also sold oil shares, spooked by a sharp fall in crude prices.

The Nikkei fell 2.1 percent to 15,789.97 in midmorning trade after hitting as low as 15,758.41 earlier, the lowest level since Feb. 24.

The dollar fell below 111.10 yen during Asian morning trade and dragged down exporter shares. Toyota Motor Corp shed 1.5 percent, Honda Motor Co dropped 1.3 percent and Tokyo Electron Ltd tumbled 2.3 percent.

Analysts said that worries that the strong yen may erode exporters' profits will likely continue to weigh on the market.

"Investors are concerned that Japanese companies are losing their 'weak-yen appeal'," said Kazuhiro Takahashi, equity strategist at Daiwa Securities. "Many people are thinking it would be difficult for exporters to forecast on-year gains in their earnings for this fiscal year."

On the other hand, Takahashi said that companies announcing shareholder returns may be bought as well as defensive shares, such as construction firms, which rely on domestic demand.

According to Nomura Securities, share buybacks exceeded 5 trillion yen in the last fiscal year ended March, marking a new record high, and will likely increase further in this fiscal year.

Fast Retailing tumbled 3.5 percent and contributed a hefty 46 negative points to the Nikkei benchmark after it said that its Uniqlo clothing stores saw a 0.3 percent fall on the year in the monthly same-store sales in March.

Inpex Corp stumbled 4.5 percent and Japan Petroleum Exploration Co declined 2.3 percent after crude oil prices fell in early Asian trading on signs of weakening gasoline demand. The declines extended falls from the previous two sessions as investors doubted that producers will be able to rein in global overproduction that has seen crude prices tumble by as much as 70 percent since mid-2014.

The broader Topix dropped 2.2 percent to 1,274.76 and the JPX-Nikkei Index 400 shed 2.1 percent to 11,496.77.

(Editing by Sam Holmes)