Authorities have detained 431 people, and the government deployed the military in the worst affected cities, France 24 reported.
Some NGOs accused police of firing at civilians.
Faced with the unrest, the government of President Ivan Duque on Sunday ordered the tax reform proposal be withdrawn from Congress, where it was being debated.
And on Monday, Colombia's Finance Minister Alberto Carrasquilla resigned, saying in a statement his continued presence "would make it difficult to build the necessary consensus quickly and efficiently" for a new reform proposal.
Despite the withdrawal of the bill, which protesters said would make Colombian poorer in the midst of the coronavirus pandemic, an umbrella group known as the National Strike Committee called for new demonstrations on Wednesday.
"The people in the streets are demanding much more than the withdrawal of the tax reform," it said in a statement.
Duque, whose approval rating has plummeted to 33 percent, has hit out at protesters' "vandalism" while the country is battling a lethal second pandemic wave.
Despite that, dozens of people were out on the streets anew Monday, protesting in the capital Bogota, the northwestern city of Medellin, Cali in the southwest and Barranquilla in the north.
Most of the demonstrations, which started last Wednesday, began peacefully before descending into clashes between demonstrators and public forces.
Defense Minister Diego Molano claimed the violence was "premeditated, organized, financed by FARC dissidents" and members of the ELN.
FARC -- the Revolutionary Armed Forces of Colombia -- leftist rebels signed a peace deal with the government in 2016 to end more than a half century of conflict, leaving the ELN -- National Liberation Army -- as the last operational guerrilla group in the country.
RHM/PR