At least 33 people have been killed in police operations against drug gangs in two Brazilian states since last week, authorities said Tuesday, triggering calls for independent investigations.

In the southeastern state of Sao Paulo, Governor Tarcisio de Freitas said police had killed 14 suspects after coming under fire during a massive anti-gang operation launched after an officer was shot dead Thursday in the port city of Guaruja.

In the northeastern state of Bahia, officials meanwhile said 19 suspects in three different cities had been killed since Friday in clashes with police.

In all the cases, authorities said police had returned fire after coming under attack.

However, the killings drew criticism from rights groups in Brazil, where accusations of abuses by security forces are frequent.

The Sao Paulo operation was launched Friday, a day after a 30-year-old police special forces officer was shot dead while on patrol in Guaruja, one of several ports that feed the Brazilian economic capital.

The state police force's internal ombudsman's office is investigating more deaths stemming from that operation, and estimates the total number could rise to 19, newspaper Folha de Sao Paulo reported.

TV channel Globo News said that locals have accused police of torturing suspects during the crackdown, dubbed "Operation Shield."

Freitas, an ally of far-right former president Jair Bolsonaro, denied Monday that officers had committed rights violations.

But "if there were abuses, they will be punished," he told a news conference Tuesday.

Leftist President Luiz Inacio Lula da Silva's justice minister, Flavio Dino, criticized the operation, saying the police reaction "doesn't seem proportional to the crime committed."

The Arns Commission, a rights group, called for an "immediate investigation" of the deaths, and Amnesty International criticized Freitas for "legitimizing police violence."

Authorities said they had arrested 32 suspects so far in the operation, including the policeman's alleged killer, and seized 11 weapons and more than 20 kilos (44 pounds) of drugs.

In Bahia, authorities said a police operation Friday had left seven people dead in the city of Camacari.

That was followed by an operation Sunday that killed eight people in a rural area outside Itatim, and another Monday that killed four in Salvador, the state capital.

Last year, 6,429 people were killed by police in Brazil, an average of 17 a day, according to the Public Security Forum, a watchdog group.