Caracas, Venezuela ? A 4-day-old general strike called to push President Hugo Chavez from office disrupted Venezuela’s vital oil industry Thursday, and the streets of Caracas filled with rival partisan crowds, leading Chavez to warn of an imminent coup attempt and urge supporters to stand by his populist government in the days ahead.

Venezuelan President Hugo Chavez says he will use the military to keep Venezuela's oil industry working through the opposition general strike, which enters its fifth day today.

The president’s warning came after the captains of seven tankers that belong to the national oil company dropped anchor and joined the strike — a defiant threat to the government’s main source of revenue. The tankers represent more than half of the company’s fleet and about 25 percent of its shipping capacity.

The captains refused to resume work even after Chavez warned that he intended to use military force to take over the idle craft and force them to haul their normal loads. Late Thursday afternoon on Lake Maracaibo, witnesses said the navy boarded the tanker Pilin Leon, which was carrying 280,000 barrels of gasoline, but it was unclear whether it took control. The other ships, which Chavez called “pirated,” apparently remained on strike.

Opposition leaders said the strike would continue at least another day, reflecting a decision to continue a financially punishing protest for as long as it takes to force concessions from the government. The announcement further complicated negotiations to end the increasingly tense standoff and raised fears of gasoline shortages and cancellation of oil shipments to the United States and other foreign customers.

Chavez, who until Thursday had dismissed the strike as a media-driven display destined for failure, said in a national address that the opposition was organizing the type of events that preceded his brief ouster in April, when street protests and an oil strike provoked a military-led coup. He called on Venezuelans “to reflect so you won’t be manipulated again,” even as he called his opponents “fascists” and “coup-mongers.”

The president’s comments demonstrated the escalating rhetoric on both sides of a broad ideological divide that has brought Venezuela, the United States’ third-largest oil supplier, to the brink of more political violence. The Bush administration is urging a peaceful and legal resolution of the crisis this time, preferably through new elections.