Three Spanish truckers unions on Tuesday dismissed a government aid package and joined a spontaneous one-week strike against rising fuel prices that is likely to aggravate a shortage of food products in supermarkets across the country.

The three truckers unions opted to join the strike after they decided a 500 million euro ($550.45 million) government support package offered on Monday was vague and not enough to compensate for the soaring price of diesel.

High energy costs, exacerbated by Russia's invasion of Ukraine, have compounded general price increases, threatening to slow the post-pandemic economic recovery and generating social discontent in many countries.

The government plan scheduled to be approved on March 29 "doesn't specify what it will comprise, how it will work and, more importantly, how much aid each trucker would get," the three unions said in a joint statement.

In the face of an increasing risk of shortages, Transport Minister Raquel Sanchez said on Tuesday the government was considering general fuel price reductions.

The three unions joined a loose group of truck drivers and small truck owners, calling itself the Platform for the Defence of Transport, that went on strike on March 14 to press demands for lower taxes and lighter regulations, saying they run the risk of "total bankruptcy".

The strike's first week caused disruption of supply chains in several industries and episodic shortages of some fresh products, such as eggs and other dairy supplies. On Tuesday, French giant Danone and Dutch brewer Heineken said they may have to curtail production because of a lack of some raw material.

Carmelo Gonzalez, the president of the country's main trade association of hauliers said the country could grind to a standstill later this week as up to 60% of drivers have walked out in some areas.

Top government officials initially dismissed the protests, saying the platform, mainly organised through social media, lacked representation, then added its members were linked to far-right groups. The Platform said it is non-partisan.

($1 = 0.9083 euros)

(Reporting by Inti Landauro, Emma Pinedo and Christina Thykjaer; editing by Barbara Lewis)