About 200 mothers wearing black gathered in an upmarket area of Lagos on Friday to deliver a letter of protest to the government when riot police surrounded them, witnesses said.
Bola Belgore, one of 17 women arrested, said: "We told them we were concerned mothers of Nigeria and we insisted on walking to government house, but they blocked the road and threw teargas in front of us and behind us. Everyone scattered."
Belgore said the group held the rally in solidarity with the mothers of the victims of the plane crash and had written to the police to request protection.
"We didn't think there could be any objection by anyone," Belgore said.
Having earlier denied that teargas was used, the police said they had apologised.
Sunday Ehindero, a police inspector-general, said: "Maybe the teargas ought not to have been used and that is why I have apologised."
He added that the rally was illegal.
The 10 December crash of a 32-year-old DC-9 aircraft operated by Sosoliso Airlines was Nigeria's second major air tragedy in as many months.
"Maybe the teargas ought not to have been used and that is why I have apologised"
The plane crashed at Port Harcourt airport and burst into flames during a storm. Among the 106 people on board were 50 children from the Loyola Jesuit College in Abuja on their way home for the Christmas break.
An investigation is under way to determine the cause of the crash.
Olusegun Obasanjo, the Nigerian president, grounded Sosoliso and another privately owned airline on Tuesday and ordered an emergency audit of all aircraft in the oil exporting country, accusing the industry of corruption.
Belgore said the rescue effort after Saturday's crash was also flawed, and exposed the dire state of emergency services in Africa's most populous country.