Enraged Chavez backers tried to break an opposition push to paralyze Caracas as the metropolitan area of 11 million people spun toward lawlessness.
Soldiers with assault rifles lined up outside a dissident police station occupied by the army as opposition marchers headed toward them to demand they leave. An armored personnel carrier and a truckload of soldiers were seen rumbling into the outskirts of Caracas.
With oil-producing Venezuela in crisis, crude prices rose on international markets.
The White House again urged Chavez to call early elections, but seemed to modify its stance by stressing -- as Chavez has insisted -- that those elections should come only under the rules spelled out in Venezuela's constitution.
Chavez has rejected demands for his resignation and early elections, saying the constitution doesn't allow them until August, the midway point in his current six-year term. He has ignored courts that have ordered him to give back seized gasoline trucks and remove soldiers from Caracas police stations. He has told military commanders that he -- not the courts -- gives their orders.
``We can't let an opposition-aligned judge ... prevent a military unit from carrying out orders from the president,'' Chavez said Sunday.
Using the slogan ``Block your block,'' the frustrated opposition launched its ``takeover of Caracas'' after a two-week strike devastated the economy but only strengthened Chavez's resolve.
``Take your street! Take your avenue! Take your plaza! Take your neighborhood! Take Caracas!'' opposition leader Jesus Torrealba yelled to supporters over Union Radio.
Skirmishes between Chavez supporters and opponents erupted in several parts of Caracas and other cities as outnumbered police officers and national guard troops desperately tried to keep them apart.
``You can't throw rocks at police!'' one officer pleaded with residents of a central neighborhood.
Above him, opposition supporters leaned out of windows banging pots and pans in protest. Officers fired rubber bullets at the buildings, breaking windows and sending residents scurrying for cover. The sting of tear gas filled the air.
The opposition also blocked major highways and arteries in several spots. Protesters tried to choke off traffic with rocks, tree branches and flaming tires.
On the Prados del Este highway, opposition and government supporters, separated only by the highway median, skirmished with rocks and bottles. Police tried to separate them with tear gas and rubber bullets.
``We're not leaving,'' said Ana Reina, a 58-year-old retired teacher, one of about 1,000 opposition supporters on the highway. ``The police never come when there's a mugging or a robbery -- just when they want to coerce us. But we're not afraid.''
Across the median, Gisela Perez, a 42-year-old street vendor, said she wasn't leaving either. She and about 200 others were defending Chavez, whose 1998 election ended 40 years of alternation between two U.S.-aligned -- and corrupt -- political parties.
``If we waited 40 years, they can wait until August 2003 for a referendum,'' she said. ``If they try to get rid of our president like this, we're going to kill one another.''
Opposition supporters planned a major march late Monday to expand on a protest that drew more than 1 million people into the streets Saturday.
``The only thing we ask of you is to call elections now,'' opposition leader Carlos Ortega said in comments directed at Chavez. ``But you are not a democrat. You do not want elections. What you want is confrontation and violence.''
The opposition resents Chavez's alliances with countries such as Cuba, Iraq and Libya, his discourse of class conflict and his mishandling of the economy.
A similar opposition campaign in April ended in violence that killed 19 people and sparked a military coup that ousted Chavez for two days. His supporters rallied when a new government dissolved the constitution and he was restored to power.
The strike has halted Venezuela's formidable oil exports, which bring in 70 percent of the country's hard currency, and ravaged an economy already battered by mismanagement and low oil prices. With Venezuela in crisis, crude oil futures climbed $1.28 to $29.72 on the New York Mercantile Exchange Monday.
Chavez has tried to break the strike by seizing fleets of striking gasoline tanker trucks and sending new crews onto ships anchored in protest.
On Sunday, heavily armed troops helped a foreign crew board the Pilin Leon, a tanker anchored in western Lake Maracaibo that has become a symbol of the strike. But the ship remained motionless Monday, and state officials said they were awaiting the arrival of another captain.
He's lower than a snake's belly.