TORONTO -- Shares of Manulife Financial Corp. fell more than 6% on Thursday after the insurer unveiled a $2.5-billion stock offering that raised capital concerns and speculation regarding potential acquisitions.

Analysts cut their targets for the stock.

“This offering raises concerns that, very recently, something on the capital front has changed (of a regulatory nature) that forced the capital raise,” Mario Mendonca, an analyst at Genuity Capital Markets, said in a note to clients.

He expects the company will retain capital to satisfy new and still-unknown capital requirements, but is not willing to suggest that Manulife’s capital issues are over.

“In our view, while this offering raises the capital buffer, it does not address the key issues with the stock, particularly Manulife’s outsized sensitivity to markets and rates,” Mr. Mendoca said.

The move has left the market wondering what has changed in recent weeks. On several occasions, including the third-quarter conference call, Manulife management had provided investors with some comfort that an equity raise was unlikely, the analyst noted, trimming his target price on the stock to $22 from $23.

The shares fell $1.23 Thursday to close at $18.95 on the Toronto Stock Exchange.

“Manulife did not go ‘half-way’ with this offering,” Jim Bantis, an analyst at Credit Suisse, said in a research note, adding that he was surprised by the move, given that management suggested it would take its time to achieve its balance-sheet goals.

Mr. Bantis trimmed his target price to $19 from $20 per share and suggested that the “unprecedented acquisition opportunities” CEO Don Guloien referred to this month may materialize sooner rather than later.

In August, Manulife cut its quarterly dividend in half to 13 cents a share, which the insurer said would save it about $800-million annually.

On Wednesday after markets closed, the company announced plans to issue $2.5-billion in common stock at $19 per share after selling $2.28-billion worth of shares in December 2008 at $19.40 each.

Late in 2008, after Manulife sought $2-billion in extra capital to top up its reserves, speculation grew that the company was considering a purchase of assets from distressed U.S. insurer American International Group or Fortis NV. Other names cited as possible targets included Lincoln National Corp., the Progressive Corp. Principal Financial Group Inc., Mercury General Corp., Ameriprise Financial Inc., the Phoenix Cos. Inc., Infinity Property and Casualty Corp., and RLI Corp.

In September of this year, Mr. Guloien said the global recession created many acquisition targets in Asia, Europe and North America. Manulife’s last major acquisition was the $15-billion purchase of John Hancock Financial in 2003.