Shares in the London Stock Exchange (LSE) have risen slightly on Thursday after the US Nasdaq stock market beefed up its holding.
Speculation is rising about Nasdaq's motives
On Wednesday, Nasdaq raised its stake in the LSE to 18.7% from its previous level of 15%.
Shares in the LSE rose 4 pence to £12.48 by the close of trade.
In March this year, Nasdaq withdrew a proposed £2.43bn ($4.2bn) bid for the LSE after the exchange rejected its takeover approach.
The LSE has also fought off interest from Australian investment bank Macquarie, and has been linked with bids from the New York Stock Exchange and Euronext.
However, on Wednesday Euronext said it was no longer interested in making a play for the London market.
The feverish interest in the LSE has seen its share price catapult from a low of 458.25p to a high of £12.59p in the past year.
Nasdaq's move increased speculation that it was considering making another takeover move for the LSE.
Analysts said that the size of Nasdaq's stake put it in a strong position in determining the future ownership of the exchange.
Richard Hunter, head of equities at Hargreaves Lansdown stockbrokers, said Nasdaq's acquisition was "clearly strategic".
Mr Hunter said if a rival suitor tabled an offer, Nasdaq could either make a profit by selling its stake for more than it bought it for, or "retain some influence over LSE because of the size of its shareholding".