Shares in Imperial Tobacco rose 8 per cent yesterday amid hopes that its proposed €11.6 billion takeover bid for Altadis, its Franco-Spanish rival, had made the UK cigarette maker vulnerable to a takeover itself.

Investors in Imperial yesterday welcomed the widely anticipated offer for Altadis, which would create an international tobacco group with an implied value of £22 billion (€32 billion). However, analysts said the strength of Imperial's share price also reflected expectations that Altria, the US cigarette group and maker of Marlboro, might acquire the group before any deal went through.

Peter Czerniawski, analyst at Dresdner Kleinwort, said: "Altria would not be able to buy a combined Imperial/Altadis because of anti-trust issues, so if they are interested in Imperial they will have to act fast."

Shares in Imperial, already buoyed by takeover speculation earlier this month, yesterday closed up 175p at £22.22.

Imperial's conditional cash offer of €45 a share was pitched at an 18 per cent premium to the price at which Altadis shares were suspended in early trading yesterday, and excludes a €0.50 dividend to be paid to Altadis shareholders next week.

Altadis, owner of the Gauloises and Fortuna brands, said its board would meet in the next few days to consider its response to the unsolicited approach. Its shares, released from suspension, briefly traded as high as €46.16, valuing the group at about €11.82 billion, but closed just above the offer price at €45.40.

A person familiar with the situation said both companies had been in informal talks for the past few months.