Mumbai, Sep 22 - The $23-billion equity swap deal proposed by Bharti Airtel and South Africa's MTN may hit turbulent weather with India's capital markets watchdog amending the merger and takeover norms involving international transactions, experts said Tuesday.

In a move that surprised the corporate sector, the Securities and Exchange Board of India (SEBI) Tuesday said the mandatory open offer norm will be triggered even if the overseas equity holdings, in the form of global depository receipts or American depository shares, exceed 15 percent of the total paid-up capital of the target company.

Earlier, the open offer was mandatory only when the acquisition of shares in the target company exceeded 15 percent during transactions entered into within the country, either through stock market operations or through preferential deals.

In the Bharti-MTN deal, the two sides proposed to exchange shares in addition to payout of cash that exceeds 15 percent.

Bharti had proposed to buy 36 percent of the South African company by offering shareholders half a Bharti share, whereas MTN was to get a 25 percent stake in the Indian telecom major for $2.