A video which appears to show an Islamic State-linked group in Algeria behead a French hostage has appeared on the internet.
Herve Gourdel, a 55-year-old hiker, was captured in Algeria on Sunday.
France has been involved in air strikes against IS militants in Iraq.
The Government will provide £12m over the next three years to deal with illegal immigrants trying to get to the UK from Calais.
Home Secretary Theresa May and her French counterpart Bernard Cazeneuve reached a deal which will also see increased co-operation between British and French law enforcement agencies.
They also agreed to do more to tackle organised gangs involved in people trafficking and smuggling.
Security and Immigration Minister James Brokenshire said the two countries would also "continue to push for action at European and international level to address the wider problem of illegal migration, of which Calais is just one very visible sign".
Former French president Nicolas Sarkozy has announced his return to politics, saying he will seek the leadership of the opposition party UMP.
President Francois Hollande said French fighter jets will soon strike against Islamic State militants in Iraq once reconnaissance missions have identified targets.
When asked when French airstrikes in Iraq would begin, he told a news conference: "As soon as we have identified targets, that means in a short time frame.
"It will be air support to protect Iraqi soldiers and Kurdish Peshmerga forces to reduce and weaken this terrorist group."
Russia's Industry and Trade Minister Denis Manturov has said that Russia could build its own warships similar to those commissioned from France, the RIA Novosti news agency reports.
France suspended delivery of two helicopter carriers to Russia last week amid security concerns about Moscow's actions in neighbouring Ukraine.
On Thursday, President Francois Hollande said the deal would depend on EU sanction in the coming weeks.
Britain will send the 9ft 'ring of steel' fences used at the Nato summit in Wales to Calais in an effort to stop illegal immigrants getting into Britain.
It would replace the "inadequate" fencing currently in place and hopefully create secure parking for legal travellers to wait without the threat of hassle from any disruption.
Immigration minister James Brokenshire said the move is part of a bid to send a message that the UK is "no soft touch" for migrants.
Writing in the Sunday Telegraph he warned would-be illegal immigrants Mr they "should be under no illusion about what awaits them if they arrive here illegally".
He said it was up to the French to maintain security and order on their own land but Britain would do what it could to help.
France should stop blaming Britain and "get its act together" and deal with growing numbers of asylum seekers in Calais, according to a former home secretary.
Lord Howard of Lympne said he had "some sympathy" with the mayor of Calais, Natacha Bouchart, but he said she was "directing her frustration and her anger at the wrong target" by threatening to blockade the port and demanding that London "take responsibility" for them.
He told told BBC Radio 4's Today programme: "The mayor of Calais ought to be directing her frustration at president (Francois) Hollande."
He added that the previous French administration under president Nicolas Sarkozy had recognised that the Schengen agreement which created a borderless zone between 10 European states, meant France had "lost control of its borders."
He added: "We have control of our borders. But it is the countries of the Schengen agreement that ought to get their act together and deal with this problem. We have retained control of our borders, and it is about time members of the Schengen agreement did the same."
Calais' deputy mayor Philippe Mignonet and the port’s immigration chief has said the area needs to be financially compensated for the the impact of English rules on migration.
What we want Cameron to do is to strongly talk to the migrants, that they won't be received and won't be accepted in England any more when they come through Calais.
Then to change the border, and transfer the border back to Dover. At the moment the English border is in Calais. The third point is to compensate financially the prejudice we suffer in Calais because of the English rules.
More than a hundred migrants were foiled as they attempted to storm a ferry bound for Britain in Calais yesterday.Read the full story ›