* Exports down 300,000 bpd in March - sources
* First major change in exports following tighter sanctions
* Iran said earlier in March exports unchanged
By Alex Lawler
LONDON, March 23 (Reuters) - Iranian oil exports have fallen significantly in March, industry sources said on Friday, as some buyers stop or scale back purchases amid tightening Western sanctions aimed at slowing Tehran's nuclear programme.
Crude exports from Iran appear to have fallen this month by around 300,000 barrels per day (bpd), or 14 percent, the first sizeable drop in shipments this year, according to estimates from industry consultant Petrologistics and an oil company.
European buyers of Iranian crude including France's Total have already stopped buying the oil, which is subject to European Union sanctions from July 1. Royal Dutch Shell is scaling back.
"We are taking less and less - very few barrels," said an official with a European oil company, until earlier this year one of the larger EU buyers of Iranian crude.
According to Petrologistics, a Geneva-based oil industry consultant, Iranian exports may amount to 1.9 million bpd in March, down from about 2.2 million bpd in February.
A source at an oil company, which still deals in Iranian crude, said the evidence pointed to an overall drop in shipments in March, seeing a decline of at least 300,000 bpd mainly because European customers are taking less.
Petrologistics is one of a number of companies which estimates oil output by tracking tanker shipments, because Iran, like many big oil exporters, does not routinely disclose how much it is supplying on a timely basis.
Iran's oil exports are difficult to track and, like those of other countries, they can fluctuate week by week. With a week to go in March, the picture may change.
"We are struggling to get the numbers nailed down," said an industry official.
Oil prices have climbed to $127 a barrel this year, just $20 short of their all-time high, as the tighter Western sanctions on Iran threaten to choke off its exports.
Some oil industry officials say Saudi Arabia is increasing shipments to compensate for lower Iranian supplies and to lower prices, which may lead to Saudi output climbing above 10 million bpd in March.
A Reuters survey estimated Saudi Arabia produced 9.85 million bpd in February. Saudi Arabia itself said on Tuesday its March output was expected to be around 9.9 million bpd.
An Iranian oil official, asked on Friday to comment on whether exports had fallen, referred to remarks earlier in March by Iranian Oil Minister Rostam Qasemi who said shipments were unchanged from last year. (Reporting by Alex Lawler; Editing by Jason Neely)