Pecker is a key witness in the case against the former US president, who is accused of falsifying business records to cover up hush-money payment
In a statement, the International Federation of Journalists said Ehtisham Kiyani was arrested on Wednesday "on false charges for allegedly bearing weapons in Islamabad's High Court".
Kiyani, who works for the TV station Channel 24, denied the charges and was freed the same day following a protest from fellow journalists.
His arrest was the latest in what appears to be a crackdown on journalists in Pakistan.
It came two weeks after authorities arrested a journalist, Bilal Farooq, in the port city of Karachi on charges of spreading hateful content against the military on social media. Two other journalists, Asad Tooq and Absar Alam, were recently charged with sedition.
Pakistani authorities did not immediately respond to a request for comment on Friday.
The International Federation of Journalists said the "arbitrary arrest of journalists and media workers on questionable and false charges is an abuse of power and the law and a direct violation of journalist rights".
Kiyani was arrested while covering a corruption case against Maryam Nawaz, the daughter of the former prime minister Nawaz Sharif.
Sharif has been in London since last November, when he was released on bail to seek medical treatment abroad. He was previously sentenced to seven years in prison on corruption and money laundering charges.
Although Pakistan's government insists it supports freedom of speech, journalists and press freedom advocates often accuse the country's military and its agencies of pressuring media outlets to quash critical coverage.
Pecker is a key witness in the case against the former US president, who is accused of falsifying business records to cover up hush-money payment
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