Kenya’s mobile-phone users rose at the fastest pace in at least four quarters in the three months through September as tariffs in the East African nation fell, the Communications Commission of Kenya said. The number of users increased 9.5 percent to 22 million in the third quarter of 2010, the Nairobi-based commission said on its website today. In the three months through June, user numbers increased 1 percent, and rose 2.6 percent and 8.4 percent in the two preceding quarters, according to data compiled by the commission. Kenya’s telecommunications regulator in August ordered mobile-phone operators to halve the rates they charge each other to transmit calls across networks. That triggered a round of reductions in call costs by companies to as low as 2 shillings (less than 1 cent) per minute.