The output growth of eight core sector industries slowed to 2.1 per cent in December 2013 due to a poor showing by coal, petroleum refinery products, steel and cement sectors.

The eight core sector industries — coal, crude oil, natural gas, refinery products, fertilisers, steel, cement, electricity — grew by 7.5 per cent in December 2012.

According to the data released by the government on Friday, the output of eight infrastructure industries in April-December 2013 grew by a mere 2.5 per cent against 6.8 per cent in the same period of the previous fiscal.

The eight core industries have a combined weight of about 38 per cent in the Index for Industrial Production (IIP).

The December IIP numbers would be released in the second week of February.

Coal output fell by 0.6 per cent in December year-on-year. Petroleum refinery production moderated by 1.7 per cent.

Steel output growth slowed down to 3.1 per cent in the month under review. Cement production increased by 1.1 per cent in December 2013 over the year ago period.

Among those which put up a good performance, crude oil registered a growth of 1.6 per cent and electricity generation grew at 6.7 per cent.

Natural gas output declined by 9.9 per cent in December.