The German captain of a charity ship said she disobeyed orders not to dock in Italy because she feared for the lives of the rescued migrants on board.
Sea-Watch 3 captain Carola Rackete apologised to the crew of a patrol boat her vessel trapped against a quayside.
She denied Interior Minister Matteo Salvini's accusation that she had tried to ram the boat in an "act of war".
Italy's government has taken a tough stance to try to clamp down on migrant rescue boats entering Italian waters.
After a two week stand-off with Italian authorities, Ms Rackete, 31, refused to obey a military vessel as she navigated towards Italy's Lampedusa island on Wednesday.
She was arrested on Saturday.
She said her decision to enter Italian waters was "not an act of violence" and that her aim was simply to get "exhausted and desperate" people on to dry land.
Mr Salvini described Ms Rackete as a "pirate" and an "outlaw". She is now under house arrest and scheduled to appear in court on Monday. She could face 10 years in prison if convicted.
Her ship had rescued 53 migrants off Libya on 12 June, in an operation organised by the German non-governmental organisation (NGO) Sea-Watch. Italian authorities later removed 13 of the passengers for health reasons.
In an interview published by Italy's Corriere della Sera newspaper on Sunday, Ms Rackete said she had not meant to put anyone in danger and had made an "error of judgement" when calculating the position of the police boat that she jutted into.
She said she had disobeyed orders because some migrants had already started self-harming and she was "afraid it would lead to suicides".
"For days, the crew had taken turns to stay on call, even at night, for fear that someone would throw themselves overboard. For those who cannot swim, that means suicide," she said.
Sea-Watch spokeswoman Haidi Sadik told the BBC that the migrants were now receiving care on Lampedusa. She insisted that Ms Rackete had followed both maritime and international humanitarian law.
"When you rescue people at sea you must take them to the nearest safe port," Ms Sadik said.
Ms Rackete did not dock in Italian waters to make a "political point", but to uphold her duty to rescue people, Ms Sadik said.
A crowdfunding appeal set up in support of Ms Rackete following her arrest, and backed by two prominent German television hosts, had raised more than €750,000 (£670,000) by Monday morning.