France has stopped 10,000 people from entering the country since last November's attacks in Paris, Interior Minister Bernard Cazeneuve said as he announced extra security measures in the wake of deadly blasts in Brussels on Tuesday.
France's borders are officially open under the Schengen agreement that waives controls between some European countries, but it has put checks in place since the Nov. 13 militant assaults on cafes bars, a football stadium and a music hall, in which 130 people died.
Cazeneuve said those extra controls involving 5,000 police had been particularly focused on its northern border with Belgium.
"In total, 220 points of entry are checked, 42 of them systematically and permanently. As a result over four months, 6 million people have been checked, and 10,000 individuals have already been prevented from entering," he told reporters.
Those who struck in Paris are believed to have planned their assault in Brussels. The prime surviving suspect from the assault in the French capital was arrested there last week.
Belgium's federal prosecutor said one of the explosions at Brussels Airport was likely to have been caused by a suicide bomber. There were two blast at the airport and another on a metro train.
Cazeneuve said that as of Tuesday he had deployed a further 1,600 police to bolster security at its borders and on public transport.
He was speaking after an emergency government meeting called by President Francois Hollande.
France has been on its highest alert status since Nov. 13 amid worries about another attack on its soil. After the arrest of Paris attack suspect Salah Abdeslam last week, police have been on alert for any reprisal action in both capitals, which lie about 315 km (200 miles) apart.