Swiss oil refiner Petroplus Holdings said lenders had frozen about $1 billion in a revolving credit facility, casting doubt over its ability to buy crude and sending its shares to a record low. The refiner said lenders had frozen uncommitted lines in the credit facility, which are critical to allowing its operating units to meet their obligations when they come due. \"This is of course a very serious situation for our company,\" the spokesman said. \"We are not able to buy crude as we would like.\" Petroplus has an additional $1.1 billion in committed credit lines but relies on the entire credit facility to buy crude, which means supply problems are likely to occur sooner rather than later, he said. \"It\'s not a problem in a couple of weeks, but it\'s much sooner than that.\" Today\'s announcement is a serious issue, as in the worst case the company would lack the funds required to maintain operations,\" Vontobel analyst Andreas Escher said in a note. \"We strongly advise investors to stay clear of the stock until a sustainable financing can be restored.\" Petroplus said it was evaluating options to maintain operations of its European refining and marketing system. \"The company intends to continue negotiations with the banks for a prompt restoration of the credit lines and is evaluating additional strategic options to maintain operations in its European refining and marketing system,\" it said in the statement. Some 13 banks are involved in the whole revolving credit facility, the spokesman said. Petroplus currently operates five refineries across Europe: in Coryton in the United Kingdom, in Antwerp in Belgium, in Petit Couronne in France, in Ingolstadt in Germany and in Cressier in Switzerland. Spokesmen for the company\'s refineries in Ingolstadt and Antwerp said the plants were operating as normal.