BOGOTA, Nov 15 (Reuters) - Colombia's coal production from January to September fell to 60 million tonnes, down 11.2 percent from the same period of 2012, the National Mining Agency said on Friday, a drop attributed to strikes at the biggest miners and guerrilla attacks on railways.

The world's No. 4 coal exporter has a nationwide target to produce 94 million tonnes of coal this year, up from 89.2 million tonnes for all of last year, but it will now take a surge in output to achieve it in the final quarter of 2013.

Colombia produced a higher 67.6 million tonnes in the first nine months of last year but disruption in the coal sector has been rife this year with strikes at its top two miners, Cerrejon and Drummond, lasting a month and seven weeks respectively.

Cerrejon, Colombia's top coal miner, is a joint venture Cerrejon between Anglo American Plc, BHP Billiton and Glencore Xstrata Plc. It said this week that hitting its 2013 production was growing more difficult.

U.S.-based Drummond is the No. 2 coal miner.

The government's royalty income from coal fell 28 percent in the first nine months of the year from that period of 2012, to 813 billion pesos ($423 million), compounded by a drop in international coal prices on top of less production.

The performance of Colombia's coal sector, which exports mainly to Europe, is important to the Andean country's economy as its second-biggest source of foreign currency.