In pics | Thousands of Colombians protest against Petro's 'tax reforms'
Peaceful marches in different cities
Peaceful marches also took place in Medellin, Cali, Armenia and Villavicencio.
Petro said in a tweet he respected protesters' right to express themselves but that his government also had a right to combat misinformation.
Petro promises 'total peace'
Petro, 62, has promised to seek "total peace" through deals with rebel groups and crime gangs and asked lawmakers to approve a tax reform which would raise an initial $5.6 billion for social programs next year.
The reform would raise taxes on those earning more than $2,259 per month, about 10 times the minimum wage, and eliminate exemptions.
Thousands oppose tax reforms
Petro has constructed a majority in congress through alliances with a range of parties. Right-wing party the Democratic Center, headed by former President Alvaro Uribe, has led much of the opposition to his proposals.
Some 5,000 people, many waving signs with slogans like "no to the tax reform", marched in Bogota, according to the mayor's office.
'Mr Petro you're going in the wrong way'
Some marchers compared Petro's governance so far to authoritarianism and said objections to his administration would mount.
"Mr. Petro you are wrong in your way of governing," said information technology worker James Duque.
Petro introduces several other changes to healthcare and land reforms
Petro has also proposed changes to healthcare, a land reform which would sell properties to poor farmers at below-market rates and reforms to voting.
"It's hurting my pension, it's hurting my healthcare, it's hurting private property, we need to respect families," said protester Francisco Arias in Bogota's central Plaza Bolivar.
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