The wife of the arrested former presidential contender, General Sarath Fonseka, says he has been "abducted" and that she has no idea where he is.
A tearful Anoma Fonseka demanded access to her husband saying she needs to hand over essential medication to him.
Gen Fonseka was detained by security forces at his office on Monday. The government says he will be court-martialled for "military offences".
Gen Fonseka was defeated by incumbent Mahinda Rajapaksa in last month's poll.
President Rajapaksa won about six million votes to Gen Fonseka's four million. But the general rejected the results and vowed to challenge them in court.
An official told the BBC the general had violated armed forces rules by engaging in politics while still in uniform and that he would be tried in a military court for this.
Military law still covered Gen Fonseka despite his retirement, officials said.
Military spokesman Maj Gen Prasad Samarasinghe told the Associated Press news agency that the general had not been cut off from friends.
"Family members are allowed to see him and he has been allowed to obtain legal advice also," he said.
'Treated like an animal'
But Mrs Fonseka said her husband had been "treated like an animal" as he was forcibly removed from his office.
She expressed shock that he had been picked up by someone of a lower rank.
Opposition politicians, who rallied around the retired military man as their presidential candidate last month, expressed their shock at the arrest and she appealed to the authorities to be reasonable in their treatment of him.
Opposition members described as "despicable" the operation in which, they said, a dozen military officers had dragged him from the room by his hands, feet and collar as he resisted.
One of the politicians present, Rauff Hakim, described the government as a "fascist" one which had now embarked on a political witch hunt.
Gen Fonseka was in charge of Sri Lanka's army when it defeated the Tamil Tiger rebels last year after 25 years of civil war.
But they fell out over who should take credit for the victory and both fought the election boasting of their roles in the war.
Shortly before he was detained, Gen Fonseka told reporters that he would be prepared to go before any international investigation into war crimes allegedly committed by Sri Lankan troops in the final stages of that war.
The Defence Secretary, Gotabhaya Rajapaksa, insists that the government is not open to any possible probe of that kind.
The BBC's Charles Haviland in Colombo says the arrest was dramatic but not unexpected and there must now be questions about whether this is the start of a bigger clampdown on the opposition.
After the election, the government had accused Gen Fonseka of divulging sensitive information to the public, and of plotting both a coup and to assassinate the president and his family.
Gen Fonseka has vehemently denied the charges.
He said he feared an assassination attempt against him and had been told that airports would not allow him to leave the country.
Thirukkural திருக்குறள் Holykural
Kural குறள் - 533
பொருட்பால் - பொச்சாவாமை
எப்பால் நூலோர்க்கும் துணிவு.
'To self-oblivious men no praise'; this rule Decisive wisdom sums of every school.
Thoughtlessness will never acquire fame; and this tenet is upheld by all treatises in the world.
Translation by Rev. Dr. G. U. Pope, Rev W. H. Drew,Rev. John Lazarus and Mr F. W. Ellis