Separately, police arrested a "radicalised" man in the city of Evreux in circumstances that were not immediately clear but which, judicial sources said, were linked to a counter-terrorist inquiry.
A dozen activists from the Greenpeace advocacy group climbed the north face of the vast metal-lattice structure, one of the world's most visited sites, to hang a banner carrying the French national motto, "Liberte, Egalite, Fraternite" (Liberty, Equality, Fraternity).
The incident exposed security concerns despite the fact that France is deploying extra police for voting day on Sunday. These come on top of thousands of police and soldiers mobilised following attacks by Islamist militants which have killed more than 230 people in France in the past two-and-a-half years.
"Above and beyond the motives, this publicity stunt, in the current climate, exposes faults in the security arrangements at the Eiffel Tower," police prefect Michel Delpuech said.
As tension mounted ahead of Sunday's vote, police arrested a man near a military base in the region of Evreux, a town west of Paris. Few details were immediately available on the arrest.
At least three in four of France's 47 million voters are set to go to polling stations throughout the day on Sunday to cast a ballot in a contest where centrist Emmanuel Macron is tipped to beat far-right National Front leader Marine Le Pen.
Delpuech said the emergency meeting would involve police as well as officials from Paris City Hall and the company that runs the tower erected in 1889 to celebrate the 100th anniversary of the French Revolution.
The tower, in the heart of the capital near the banks of the Seine river, attracts nearly 7 million visitors a year, not far short of 20,000 a day on average, according to its operators.
A dozen Greenpeace activists were detained for questioning, police sources said.
Greenpeace said a dozen activists were involved, hoisting a 300-square-metre banner at around 7.45 a.m, which is before normal business hours but well after dawn has broken at this time of year.
"We wanted to say we are against the rise of nationalism and authoritarianism in France and in other countries," Greenpeace France's head, Jean-Francois Julliard, added on public radio station francinfo.
The action came on the last day of campaigning, when Le Pen paid a surprise visit to a Roman Catholic cathedral in the northern city of Reims, where a group of teenagers hostile to her views turned up to jeer and throw eggs, according to TV images from the scene.
French news channel BFM TV showed footage of her right-hand man being rushed to a car amid both jeers and cheers from mostly young bystanders near the gothic-style Notre Dame cathedral of Reims where many of France's kings were coronated.
Le Pen herself was, according to BFM and photographs posted on social media, spirited away from the cathedral zone, flanked by bodyguards, head bowed.
Voters will flock to more than 10,000 polling stations around France over a period of 10 or 12 hours on Sunday before preliminary estimates of the result are announced at around 8 p.m., or 1800 GMT.
(Additional reporting by Emmanuel Jarry, Andrew Callus and John Irish; Writing by Brian Love; Editing by Richard Balmforth)
Get Breaking news, live coverage, and Latest News from India and around the world on NDTV.com. Catch all the Live TV action on NDTV 24x7 and NDTV India. Like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.