Ranbaxy's shares rose by 0.65 per cent on Thursday to close at Rs 493.55 a share, below the offer price of Rs 737 a share.
Two days ago, it had been reported that institutional investors Life Insurance Corporation and General Insurance Corporation, which between them hold 16.43 per cent in Ranbaxy, offered to sell their stake.
In June, Daiichi Sankyo entered into a deal with Ranbaxy to acquire the 34.8
per cent stake held by Malvinder Mohan Singh's family, the promoters.
Daichii Sankyo's plan was to acquire up to 92.1 million shares through the open offer to have a controlling majority stake in the pharmaceutical major with a cumulative stake of about 55 per cent.
Last month, the Foreign Investment Promotion Board had approved the acquisition of Ranbaxy by Japan's Daiichi Sankyo.
