He said fighting between Muslim and Christian communities in the northern city of Kaduna could have started at any time and blamed an article which was offensive to Muslims for provoking the violence.
The riots broke out last week after the newspaper ThisDay defended Miss World against its Muslim detractors and implied the Prophet Mohammed would have enjoyed the show.
Mr Obasanjo told an American TV network he was sad to see the departure of the Miss World contestants who will now stage their pageant in London in December.
'No regrets'
Calm has now returned to the city and mass funerals have begun for more than 200 people known to have died in the four days of rioting.
Court cases against the alleged killers have started.
The Lagos-based paper which printed the story has retracted it and apologised, but President Obasanjo appeared not to be satisfied.
"Irresponsible journalism in Nigeria bears responsibility," he said.
"What happened obviously could have happened at any time."
But the president said he had no regrets about his country's attempt to host the show - a right won last year when Nigerian Agbani Darego became the first black African to be crowned Miss World.
"I am sorry that they had to leave Nigeria," he said of the contestants and organisers.
"They were guests within our gates and we did everything possible to show that we are good hosts and hostesses in Nigeria."
Curfew enforced
The Red Cross said 215 bodies had been counted on Kaduna's streets and in mortuaries and correspondents say the death toll could rise yet further.
Reports from Kaduna say sporadic violence has continued and that security forces are working to maintain a curfew imposed on the city, which has a large Christian minority.
Some shops, schools and banks reopened on Monday as the funerals began and as hundreds of people arrested during the riots started to appear in court.
Muslim defendants are being tried by the Islamic court of Kaduna State, while Christians will appear before civilian jurisdictions, the spokesman for the governor of Kaduna State, Maktar Sirajo, told the French news agency AFP.
It is estimated that more than 1,000 people were injured and more than 11,000 made homeless in the clashes.
Civil rights activists said more than 20 churches and eight mosques had been burnt down in the city as well as a number of hotels.
They also said there had been allegations that some members of the security forces had killed civilians without provocation.
Two years ago, Kaduna saw more than 2,000 deaths in clashes between Christians and Muslims.
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