Saudi Arabia's Yanbu National Petrochemical Co (Yansab) posted a 31 per cent slump in fourth-quarter net profit on Monday, citing a shutdown at its plant for the decline.

The firm made a net profit of 442.2 million riyals ($117.9 million) in the three-month period to December 31, it said in a bourse filing, down from 640.8 million riyals during the same period of 2012.

The earnings were well below the average forecast of seven analysts polled by Reuters, who expected a net profit of 619.3 million riyals for the quarter.

Yansab attributed the fall to the shutdown of its complex and an increase in its Zakat payment. Zakat is a charitable donation which firms in Saudi Arabia are obligated to pay.

Yansab, a subsidiary of Saudi Basic Industries Corp , was forced to shut its petrochemicals complex for three weeks for maintenance at the end of October due to a problem with a water cooling network.

It estimated the financial loss from the shutdown, at the time, as 160 million riyals.

Full-year profit for 2013 was higher year-on-year. Yansab reported a net profit of 2.64 billion riyals, versus 2.45 billion riyals in 2012, citing higher prices for its products and lower financing costs. - Reuters