Top global oil exporters including Russia and Saudi Arabia agreed on Tuesday to freeze output to tackle a global glut but said the deal was contingent on other producers, with Iran absent from the meeting and planning to ramp up shipments. The Saudi, Russian, Qatari and Venezuelan oil ministers visited Doha for a previously undisclosed meeting - their highest-level discussion in months on joint action to help prices recover from their lowest in more than a decade. Ali al-Naimi, the Saudi Arabian oil minister, said that freezing production at January levels was an adequate measure ...