* Refinery workers stay on strike, truckers slow roads
* Government says will not permit industry blockades
PARIS, Oct 18 (Reuters) - French truck drivers staged go-slow operations on highways, rail strikes intensified and petrol stations ran out of fuel on Monday as protests gathered pace ahead of a Senate vote on an unpopular pension overhaul.
The government, which has stood firm on President Nicolas Sarkozy's plan to raise the retirement age through months of protests, assured the public infrastructure would not freeze up despite a week-long strike at refineries that has forced hundreds of petrol stations to close.
Rail services were also badly disrupted as strike action ramped up ahead of a fresh nationwide protest on Tuesday in what threatens to be a make-or-break week for Sarkozy over his reform.
Government ministers are stressing the country has plenty of fuel and that airports in particular have ample supply.
"The government is in control," Industry Minister Christian Estrosi told RTL radio on Monday. "There will be no blockade for companies, no blockade for transport and no blockade for road users."
Workers at France's 12 refineries continued their strike on Monday, a CGT union official told Reuters, and protesters blocked access to some fuel depots in the south.
France's UFIP oil industry lobby has said France could see serious fuel supply problems by mid-week, meaning the government may have to look at tapping emergency reserves.
A majority of French support protests against planned legislation to raise the minimum and full retirement ages by two years to 62 and 67 respectively, a measure the government says is the only way to stem a ballooning pension deficit.
The main points of Sarkozy's bill have passed through both houses of parliament and following a Senate vote scheduled for Wednesday on the full package, the bill could soon be signed into law.
Truck drivers used vans from Sunday evening to slow the flow of traffic on motorways around cities like Lyon and Rennes, but had not yet resorted to using large trucks to block roads.
Prime Minister Francois Fillon has warned protesters that blockading vital infrastructure is illegal.
"The right to strike is not the right to bar access to a fuel depot, that's an illegal action," Fillon told TF1 television on Sunday. "I will not let the French economy suffocate from a blockage of fuel supply."
Sarkozy was due to hold talks later on Monday in the northern seaside resort of Deauville with his German and Russian counterparts Angela Merkel and Dmitry Medvedev. (Reporting by Catherine Bremer and Brian Love; Additional reporting by Muriel Boselli; Editing by Louise Ireland)