Self-storage operator National Storage REIT has bought a stake in its listed rival Abacus Storage King, in a move that could potentially thwart a $1.9 billion takeover proposal for it by a South African billionaire.

Known by its ticker NSR, the operator has taken 4.78 per cent stake in its Abacus-run rival, which this month received a conditional takeover proposal from a consortium formed between Nathan Kirsh’s family office, Ki Corporation, and New York-listed giant, Public Storage.