France election | Hollande appeals to Le Pen voters

Hollande won the first round of the election, narrowly beating conservative Nicolas Sarkozy, while the National Front's Marine Le Pen came third.

Sarkozy, who faces a run-off election with Hollande on 6 May, said he had "heard" Le Pen voters.

Uncertainty over France's future direction unsettled markets on Monday.

Sterling stayed close to a 20-month high against the euro on Tuesday and was seen poised for more gains, with political turmoil in another important eurozone state, the Netherlands, adding to investor fears.

On Sunday, Sarkozy became the first president in modern French history to lose the first round of his re-election campaign.

Hollande came top with 28.6%, Sarkozy took 27.1% and Le Pen 17.9%.

Le Pen's score was a huge advance on the 10.4% registered by her father, National Front (FN) founder Jean-Marie Le Pen, against Sarkozy in 2007.

Speaking to left-of-centre French daily Liberation, Hollande said it was up to him to persuade FN voters.

"There is the Le Pen electorate, part of whom come from the left and should be on the side of progress, equality, change, shared effort and justice, because it is opposed to privilege, financial globalisation and a failing Europe," he said.

"It is up to me to convince them that the left defends them."

Such voters did not necessarily adhere to "FN ideas and its obsession with immigration in particular", the Socialist candidate argued.

"Above all, they are expressing a social anger."

Le Pen and her party advocate abandoning the euro, reinstating border controls, cracking down on immigration and stamping out what they perceive as attempts to "Islamise" France, which has Western Europe's biggest Muslim minority.

If turnout at the second round is similar to that in the first, when 80% of voters participated, both Hollande and Sarkozy must win over FN votes to be sure of climbing above the 50% mark needed to win the presidency.

Hollande is expected to pick up much of the support for far-left candidate Jean-Luc Melenchon, who won 11.1% of the vote, but the 9.1% who backed centrist candidate Francois Bayrou are divided in their affections, opinion polls suggest.

Analysts say it is extremely unlikely Le Pen will endorse either candidate in the second round, though she has said she will make her views known on 1 May.