Sony Corp. and Nikon Corp. were among several manufacturers that shut plants following Thursday night's 7.1-magnitude earthquake, delaying their recovery from last month's historic temblor.

Sony, Japan's largest exporter of consumer electronics, said it suspended operations at two plants in Miyagi Prefecture after the earthquake, an aftershock of the 9-magnitude temblor on March 11, caused power outages. Nikon Corp., Fujitsu Ltd., Tokyo Electron Ltd. and NTT DoCoMo Inc. also reported disruptions Friday.

The aftershock, the strongest to hit Japan since March 11, sets back the recovery as manufacturers from Sony to Toyota Motor Corp. reel from last month's disaster that killed thousands, knocked out plants, triggered a nuclear crisis and caused electricity shortages. The damage from the initial disaster may total as much as ¥25 trillion, or 0.5 of the economy, the government has estimated.