SAO PAULO (AFP) - Wearing a camouflage T-shirt that clings to his biceps, Brazilian policeman Saulo packs his bag with combat boots, camping gear, gun holsters and a knife - "just the essential" to go fight in Ukraine.

The 35-year-old Sao Paulo man quit his job as a military police officer to travel more than 11,000km and join Ukraine's fight against the Russian invasion.

"I identify with the cause, with the Ukrainian people who are suffering the injustice of a foreign aggressor," said Mr Saulo, who asked that his last name not be used for security reasons.

"And I want to help avoid World War III," he told AFP, laying the items on his short packing list out on his bed alongside his black duffel bag.

Picking up a small Brazilian flag, he added it to the pile.

Although President Jair Bolsonaro has said Brazil will remain "neutral" over the conflict - drawing criticism in some quarters - hundreds of Brazilians have taken steps to go fight in Ukraine.

They are looking to join the 20,000 volunteers from more than 50 countries who have applied to join the International Legion of Defence of Ukraine, a corps launched to help fend off the invasion, according to figures from the Ukrainian Foreign Ministry.

Mr Saulo said good-bye to his partner and two children and left on Wednesday (March 23) for Poland, where Brazilians already on the ground have promised to help him join the war.

He bought the one-way ticket with his own money.

Mr Saulo said he made his decision after seeing images from Ukraine of bombed-out residential buildings and hospitals. That convinced him to answer President Volodymyr Zelensky's appeal to join the new foreign legion and fight "elbow to elbow" with the Ukrainian army.

"There's a risk I won't come back. Anyone who goes over there knows that. We're not little kids," said Mr Saulo, who sports a tattoo of a big black skull on his right arm, a knife clutched in its teeth.

His only fear, he said, is the conflict "erupting into nuclear war".

Defending a foreign country

The Ukrainian foreign legion's only requirement to join is military or firearms experience, according to representatives who are helping organise the effort.

Other webpages set up for Brazilians rallying to the cause have hundreds of members, such as Portuguese-language Facebook group "Volunteers to Fight in Ukraine", with 1,800.

The site is a forum for would-be volunteers to swop information - though members told AFP they limited their interactions, fearing Russian spies could be watching.

One would-be volunteer, Guilherme - his name was changed for safety reasons - said he saw going to the front as a way to make a fresh start in life.

The 29-year-old formerly served in the Brazilian army and the French Foreign Legion, then worked as a private security guard in Rio de Janeiro, but is now unemployed.

"Things are hard here in Brazil," he said.

"Helping in Ukraine is an opportunity... We have to think about what we can do to help others in this world, and not just say 'That's not my war,' because the world's ending".

'Open arms'

Ukraine's consul in Sao Paulo, Mr Jorge Rybka, said would-be volunteers receive "no assistance of any kind" from the Ukrainian government.

Brazil's Foreign Ministry, meanwhile, said it "emphatically discourages" people from travelling to Ukraine given the security situation.

That did not stop Brazilian military veteran Leandro Galvao, who is already on the ground in the suburbs of Kyiv, where he carries out patrol and civilian rescue operations alongside the Ukrainian army.

Mr Galvao, 49, came from Estonia, where he lives, to "defend democracy", he told AFP.

"Ever since I joined the Ukrainian army, I'm part of this nation, and I'll defend it to the end," said the Sao Paulo native, who has two children.

Foreign fighters, he said, "are welcomed here with open arms, with happiness and thanks".