Workers of Royal Dutch Shell in the Netherlands began a phased shutdown of Europe's largest oil refinery on Monday in a dispute over pensions, AP reported. A demonstration by hundreds of workers failed to end the stalemate before the 6 p.m. (1700gmt) deadline set by the unions for launching strikes at two Dutch installations. Workers began scaling back production at the refinery at Pernis, which processes 412,000 barrels of crude oil per day, and were to take further action at a petrochemical complex at Moerdijk which converts oil products into chemical products at the rate of 10,000 tons per day. The strike was restricted to the Dutch facilities of the global petroleum empire. The unions said it would take several days to cut production for safety reasons. The workers are resisting changes in the pension plan for about 9,000 Shell employees and another 1,800 workers at a Shell subsidiary, NAM. The union says it wants workers to have the option to retire at age 60 through a new savings plan proposed by the Dutch government, but says the company is refusing to go along with the plan. Shell says that giving in to union demands would add 9 percent to the company's labor costs. In a separate development, Shell announced the final terms to buy shares from investors still holding shares in the company's Dutch arm ahead of the planned merger of the Dutch and British units on Dec. 21. These shares represent ¤1.6 billion (US$1.92 billion) in share capital, Shell said. Dutch holders will be given ¤52.21 (US$62.96) per share, while holders of New York-registered shares will be paid the dollar equivalent at the exchange rate on Dec. 20. British shareholders may choose for Royal Dutch Shell shares or cash, the company said.