Nifty Corp., a leading Internet service provider owned by Fujitsu Ltd., plans to compensate more than 10,000 subscribers for system problems that occurred over the summer with its asymmetrical digital subscriber line service, company officials said Tuesday.

Nifty experienced small intermittent problems from May to July, causing its ADSL service to be down for 27 hours in May, 13 hours in June, and three hours in July.

Vouchers for Nifty's various services, worth from 352 yen to 467 yen, will be sent in compensation, they said.

Recently, intensified competition in the ADSL market has led to more glitches, but it is rare for an Internet service provider to compensate customers.

The cause of the trouble has already been sorted out, the company said.