UK airports group BAA has rejected a hostile £8.75bn bid from Spanish construction group Ferrovial.
BAA shares have surged about 30% since the February offer
The offer is at the same 810p a share that BAA rejected from Ferrovial on 17 March, saying it undervalued the firm.
BAA is the UK's largest airports operator and runs London's Heathrow, Gatwick and Stansted.
The UK Takeover Panel had given Ferrovial until 24 April to make a formal bid for BAA or walk away from any deal for six months.
"We have already made our position on this offer crystal clear," said Marcus Angus, BAA's chairman.
In a statement, BAA said the offer was "at the same price that the board has already emphatically rejected as not beginning to reflect the true value of BAA's unique portfolio of strategic airport assets".
BAA shares closed up 1.5% at 847p.
The rise suggested that investors either thought BAA was going to get a better offer, or that it would try to return some cash to shareholders in order to gain their support against a takeover bid.
"We fully support the board's rejection of the cash offer at 810p from Grupo Ferrovial," said Robert Waugh, head of UK equities at Scottish Widows Investment Partnership (SWIP), which owns about 3.4% of BAA.
'Keen to talk'
Ferrovial is making the hostile bid at the head of a consortium that also includes Canadian investment fund Caisse de Depot et Placement du Quebec, and Singapore government fund GIC.
"Whilst this bid is being made unilaterally, we do not regard it as hostile," said Ferrovial chairman Rafael del Pino.
"We remain keen to engage in a dialogue with the BAA board with a view to securing a recommendation for the consortium's offers."
Ferrovial said that debt financing for the proposed takeover had come from Citigroup, Royal Bank of Scotland, Santander, HSBC and Calyon.
It added that it was committed to "safe long-term funding" in the bond markets, and planned to consult with BAA's existing bondholders to help develop its long-term funding plans.
Ferrovial currently owns Belfast City airport and 50% of Bristol airport.
European airports are attracting investors who are looking to benefit from the predicted doubling in air passenger traffic over the next 15 years.
BAA recently fought off other bidders when it paid the Hungarian government $2.2bn for control of Budapest airport.