The CGT union, a confederacy of French trade unions, said that more than 95 per cent of workers were on strike in the refineries and that all depots were blocked off.
Hundreds of workers are occupying the plant near Dunkirk after stampeding onto the site on Tuesday and breaking into administrative offices to protest against the site's possible closure.
Total officials said last month they were studying a permanent closure of the refinery, which employs 370 people directly and 450 sub-contractors.
Union activists said they were counting on support from other Total workers.
"We are very determined but we will not succeed in moving things forward if we are alone," Patrice Leclaire, a union official, said.
A meeting of the works committee is scheduled for March 29 at which Total is to present its future plans for the plant.
The oil company has come under pressure from the French government to guarantee jobs after Nicolas Sarkozy, the French president, said this month that fighting unemployment was a priority.
Total last week reported profit of $10.9bn in 2009, down 44 per cent from the previous year.