The number of mobile-telephone subscribers in Colombia fell to 42.03 million at the end of December, down 0.7% from 42.34 million at the end of September as the largest operator, Comcel SA, owned by Mexico's America Movil SA (AMX), lost customers, the country's antitrust agency said Monday.

Comcel, the Colombian unit of Mexico-based America Movil, still held the biggest slice of the market with 28.87 million subscribers, down from 29.53 million at the end of September, the regulator said. Comcel controlled 69% of the Colombian market, down from 69.7% three months earlier.

In a statement, Comcel attributed the decline to "a revision and cleaning of its [subscribers] database."

There are about 45 million people living in Colombia.

Comcel lost market share to its competitors, the local units of Spain's Telefonica (TEF) and Millicom Internacional Cellular (MICC).

Telefonica reported 8.96 million subscribers at the end of December, up from 8.81 million subscribers at the end of September. The market share of Telefonica in Colombia is 21%, up from 20.8% at the end of September.

Colombia Movil SA, the local unit of Millicom, had 4.19 million subscribers, up from 4 million at the end of September. The country's third-largest operator saw its market share rising to 10% from 9.5%.

The total number of subscribers in Colombia at the end of December 2009 was 3.2% higher than at the end of December 2008.

-By Inti Landauro, Dow Jones Newswires; 57-1-694 00 76; colombia@dowjones.com