Docomo blames mobile network trouble on overseas call switches.

TOKYO, Aug. 7 Kyodo

NTT Docomo Inc. said Tuesday that large-scale malfunctioning of its mobile phone network last week was caused by a problem in NTT Communications Corp.'s switching gear for international telephone services.

NTT Docomo will create a system to insulate its cellphone services from such problems in other companies' facilities, Senior Executive Vice President Fumio Iwasaki said at a press conference.

Last Thursday, the switching system of NTT Communications caused a failure affecting NTT Docomo's international roaming service that enables people to use their cellphones abroad, according to Iwasaki.

Trouble then developed in NTT Docomo's network, temporarily hampering the voice and e-mail communications of up to 1.45 million subscribers in parts of Japan.

The Ministry of Internal Affairs and Communications  has told NTT Docomo to take measures to prevent the recurrence of failures that have successively taken place at its service network since January.

"We deeply apologize for having caused our customers a great deal of trouble," Iwasaki said.