* April-Sept Iranian oil share in Indian imports about 11 pct

* India Sept Iran oil imports 552,200 bpd; Jan-Sept at 412,000 bpd

* Apr-Sept Iran oil imports near 468,000 bpd vs 261,000 bpd yr ago

NEW DELHI, Oct 12 (Reuters) - India's purchases of Iranian oil fell 4.1 percent in September, slipping from August when imports from Tehran hit their highest in at least 15 years, according to ship tracking data and a report compiled by Thomson Reuters Oil Research and Forecasts.

India, Iran's top customer after China, still imported about 552,200 barrels per day (bpd) of oil from the Persian Gulf nation in September, more than double the same month a year ago following the end of sanctions targeting Tehran in January.

India's oil imports from Tehran in January-September grew 90.5 percent to an average 411,900 bpd oil, the data showed.

Iran has been boosting oil shipments to recoup market share ceded to rivals Saudi Arabia and Iraq.

The OPEC producer's total crude oil and condensate sales likely reached around 2.8 million barrels per day in September, two sources said, nearly matching a 2011 peak in shipments before sanctions were imposed.

India's average Iranian oil imports in April-September, the first six months of India's financial year, rose nearly four-fifths to about 468,000 bpd, the data showed, with Tehran's share in overall purchases jumping to 11 percent, just below pre-sanction levels.

Average imports over the period were at their highest in at least 15 years, the data showed.

India, the world's third-biggest oil importer, shipped in a record about 4.47 million bpd oil in total in September, about 4.4 percent more than the previous month.

State-run Mangalore Refinery and Petrochemicals Ltd was the biggest importer of Iranian oil in September buying about 150,200 barrels per day, the data showed.

Essar Oil imported about 134,000 bpd followed by 131,000 bpd by Indian Oil Corp and 69,000 bpd by Reliance Industries Ltd. Hindustan Petroleum imported about 68,000 bpd oil.

By Reuters