BEIJING, March 5 (Reuters) - China's state-run iron ore buyer has widened restrictions on buying new seaborne iron ore cargoes from BHP BHP.AX as a months-long contract dispute drags on, people with knowledge of the matter told Reuters.

China Mineral Resources Group (CMRG) told several traders this week to buy fewer seaborne cargoes of BHP's flagship products: Mac fines, Newman fines and Newman lumps, according to two people who spoke on condition of anonymity given the sensitivity of the matter.

These products have not yet been subject to the widely reported restrictions introduced in September and November.

BHP declined to comment, while CMRG did not immediately respond to a Reuters emailed request for comment.

Several traders said sales of BHP cargoes were unusually low since last week, a move they attributed to growing concern in the market about a bigger clamp-down from the state-run buyer.

CMRG, set up in 2022 to centralise iron ore buying and win better terms from miners, barred domestic steel mills and traders from buying BHP's Jimblebar fines, a type of iron ore, in September.

It extended the ban in November to Jinbao, another variety, as negotiations dragged on.

That month, two iron ore traders told Reuters they were ordered by CMRG to seek permission before buying any BHP seaborne cargoes. They have since applied for permission and received no response.

Stocks of Jimblebar cargoes have piled up at some major Chinese ports to a record high of 9.8 million tons by February 26, a whopping rise of 457% from late September, according to two separate trade sources with knowledge of the matter.

Bloomberg reported the story first.

(Reporting by Reuters staffEditing by Tomasz Janowski)