A consortium led by South African billionaire Nathan Kirsh may need to increase its $1.9 billion takeover offer for Abacus Storage King after a rival operator bought a small stake in the self-storage player, potentially blocking the proposed buy-out, according to analysts.

The surprise move this week from National Storage REIT – known by its ticker NSR – gives it a beachhead of near 4.8 per cent in the register of its listed rival. But, as analysts were quick to note, a takeover transaction could be blocked with a stake of just 10 per cent, or even less.