A policeman tried to search the attacker as he approached the press club's gate, but the man resisted and was able to trigger his explosives, killing the officer and an accountant who worked for the organization, said Peshawar's police chief, Liaquat Ali Khan.
A woman who was at the site of the attack apparently died of cardiac arrest, said Sahib Gul, a doctor at a hospital in Peshawar where the three bodies were brought.
Adil Khan, a local photographer who was inside the press club when the attack occurred, said he heard the police officer at the gate, Muhammad Riaz, trying to force the bomber to submit to a search.
"Suddenly a big explosion occurred and smoke made me unable to see immediately what happened," said Mr. Khan. "After a while, I saw Riaz and accountant Mian Iqbal lying dead in a pool of blood and there were some scattered body parts."
Seventeen other people were injured in the attack, many of whom were traveling in a bus that passed the press club when the explosion occurred, said Dr. Gul.
The blast blew out the press club's windows and slightly damaged the gate and several surrounding buildings.
Peshawar has been hit by at least seven attacks in the past two months in retaliation for a military offensive launched in mid-October against the militant stronghold of South Waziristan in Pakistan's lawless tribal area near the Afghan border.
A single attack in late October in a market popular with women and children in Peshawar killed 112 people.
The Peshawar Press Club targeted in Tuesday's attack is a well-known landmark in the city, and many journalists congregate there.
"Journalists have played a vital role in our war by exposing the terrorists, so they are on the target list too, like mosques, bazaars and security institutions," said Mian Iftikhar Hussain, the information minister for Northwest Frontier Province, where Peshawar is the capital.
A provincial labor minister was scheduled to hold a press conference at the press club later Tuesday, said the organization's president, Shamim Shahid.
He praised Mr. Riaz, the police officer who prevented the bomber from entering the building.
"The policeman averted a major incident by sacrificing his life," said Mr. Shahid.