The Oil Ministry website Shana quoted Rostam Qassemi on Thursday as saying the Organization of Petroleum Exporting Countries \"should produce up to 30 million barrels per day (as a group), but some countries, including Saudi Arabia don\'t observe these regulations.\" OPEC in December agreed to the collective ceiling of 30 million barrels a day in December, but the group\'s daily production is now higher by over a million barrels as Saudi Arabia replaces oil from sanctions-hit Iran, a Bloomberg report said.\"As an OPEC member, we enjoy the right to protest\" against overproduction by a member, Qassemi said. Meantime, Qassemi Monday accused Saudi Arabia of trying to replace its oil, a policy he said will fail. Qassemi said Iran has already halted supplying oil to UK major Royal Dutch Shell PLC (RDSA) because the Anglo-Dutch oil giant was unable to settle its debts. The minister also said \"Greek authorities had problems with payment\". To fill in the gap, Saudi Arabia - the world\'s largest oil exporter - has hiked production to 10 million barrels a day, its highest level in three decades. In the last days of 2011, Washington imposed new sanctions on Iran to penalize countries for importing Iranian oil or doing trade with its central bank. The US extraterritorial laws and pressures forced the EU member states to ratify in their meeting on January 23 and after months of debates to sanction oil imports from Iran and freeze the assets of Iran\'s Central Bank within the EU. Later, Tehran summoned the ambassadors of Italy, Spain, France, Greece, Portugal and the Netherlands to protest at the EU\'s unilateral sanctions against Tehran over its peaceful nuclear program, and warned them that it would soon stop oil exports to these countries if they do not reverse their decision. After the EU\'s decision to embargo Iranian oil supplies, Tehran stopped exports first to France and Britain and very recently to Greece and Spain. Following Tehran\'s oil sanctions against the three and its warning to other EU members, oil prices started soaring in the world markets. Meantime, demand is growing for Iranian crude oil in Asian and African markets after the EU\'s fresh decision.