Veteran journalist and columnist Waris Raza was allegedly "abducted" from his residence in Karachi in the early hours of Wednesday before being released in the evening, according to his colleagues and media organisations.
Arif Raza, a brother of Waris, confirmed that he had returned home in the evening.
Earlier, Waris's daughter Laila Raza in a tweet alleged that her father had been abducted by "law-enforcement agencies".
"They want to suppress all progressive voices! My father has done nothing but speak truth to powers that be!" she wrote.
Waris has over 30 years of experience in print and electronic media and was presently working as a columnist for Urdu daily Express, according to his friends.
He also recently compiled a book about the 70-year struggle of the Pakistan Federal Union of Journalists (PFUJ) for press freedom in the country.
Karachi Union of Journalists (KUJ) general secretary Fahim Siddiqi said law-enforcement agencies personnel had arrived at Waris's home in Sahafi Colony in Gulshan-i-Iqbal at around 2:45am and taken him away. The security personnel told the family members they would release him after a short while.
According to Siddiqi, Waris made phone contact with his family at around 6:50am, informing them that "he was coming." His whereabouts were not known since then.
The KUJ, of which Waris is a member, stated that he had been "shifted to an unknown location" after being taken into custody.
Both KUJ and PFUJ condemned Waris's detention by law enforcers and demanded his immediate release.
KUJ president Nizamuddin Siddiqi, general secretary Fahim and members of the executive council in a statement noted Waris's contributions to journalism, saying he had remained part of every struggle for media freedom and freedom of expression.
“His arrest is a matter of concern and the KUJ considers it an attack on media freedoms,” the statement.
Separately, the PFUJ gave a call for countrywide protests against Waris's detention and announced that journalist bodies would hold protests across the country on Thursday.
PFUJ president Shahzada Zulfiqar and secretary general Nasir Zaidi in a statement said the "arrest of a responsible journalist like Waris Raza is a matter of grave concern".
They said that at present, every voice being raised for media freedom and freedom of expression was being suppressed.
“If the government thinks the arrest of some persons and registration of cases will pave the way for legislation of draconian laws, it is their illusion,” the PFUJ stressed.
The KUJ, meanwhile, announced that it would organise a rally outside the Supreme Court's Karachi Registry on Thursday morning to record its protest against Waris's arrest and draw the attention of the chief justice of Pakistan over his enforced disappearance.
Senior Superintendent Police (SSP)-East Qamar Raza Jiskani told Dawn that police had not received a complaint from Waris's family over his alleged abduction.
Politicians and journalists too condemned Waris's arrest, with #ReleaseWarisRaza trending on Twitter in Pakistan.
"This country is not safe for journalists, activists, anyone who dares to speak out," journalist Zebunnisa Burki tweeted.
MNA Mohsin Dawar said Waris's "abduction shows the vulnerability of anyone daring to disagree with state's narrative".
"The ordeal of thousands of missing persons has begun similarly. Their families tortured by the uncertainty, at times for decades. This is a despicable practice."
Researcher and Awami Workers Party Punjab President Ammar Rashid acknowledged Waris as "a senior progressive journalist & writer with impeccable credentials who has consistently used his pen to highlight injustices that otherwise remain unheard".
Demanding his immediate release, Rashid said the abduction was "illegal & unconstitutional".
PPP leader Farhatullah Babar termed reports of Waris's kidnapping "highly disturbing".
"Waris Raza must be safely recovered urgently & perpetrators named, shamed and prosecuted. Everyone must raise voice," he tweeted.
Journalist Hamid Mir said he "strongly condemn[s]" the journalist's arrest.