TOKYO, March 1 (Reuters) - Japan's Nikkei share average fell to a one-week low on Thursday morning, with precision machinery makers hit by the euro's weakness against the yen and most sectors in negative territory.

The Nikkei dropped 1.7 percent to 21,684.72 in mid-morning trade, its lowest since Feb. 22.

The broader Topix declined 1.6 percent to 1,739.62.

Investors were worried about the yen's strength against the euro, adding to overall risk aversion.

The euro dropped to 129.86 yen, its weakest level since early September after benign inflation data in the euro zone dented expectations that the European Central Bank will dial back its stimulus.

Precision equipment makers Omron Corp and Terumo Corp, which have a relatively big exposure in Europe, fell 2.8 percent and 3.0 percent respectively.

Other exporters were also sold down, with Toyota Motor shedding 1.9 percent and Honda Motor falling 1.1 percent. (Reporting by Ayai Tomisawa; editing by Richard Pullin)