Police in Pakistan have released a photograph of the man they say carried out a suicide bomb attack on the convoy of ex-Prime Minister Benazir Bhutto.
There is anger and grief in Karachi
At least 130 people died in Thursday's twin blasts in Karachi, hours after Ms Bhutto ended her self-imposed exile.
Ms Bhutto, who escaped unhurt, told the BBC she would never give in to the militants and was determined to fight general elections due in January.
The carnage has raised questions about the safety of campaigning for the poll.
Ms Bhutto heads the country's largest political force, the Pakistan People's Party (PPP). She has been negotiating with President Pervez Musharraf over a possible power-sharing deal.
The US has backed such an accord, amid concerns about the military's inability to defeat Islamist militants and Gen Musharraf's rising unpopularity.
Newspapers in Pakistan carried photographs of the head of the suspected suicide bomber propped up on a white sheet.
The man looks to be in his 20s, unshaven with curly hair and hazel eyes. The BBC's Barbara Plett in Karachi says it is believed he was an Islamic militant.
Police have not said which group sent him.
President Pervez Musharraf has asked officials for the results of an urgent preliminary inquiry by Monday.
No-one has admitted targeting Ms Bhutto's triumphal procession through Karachi.
Pro-Taleban militants, who have threatened to send suicide bombers to kill her, are the prime suspects, although she has accused ex-army officials of involvement, too.
Our correspondent says Ms Bhutto, who has been planning a political comeback, is working out her next steps after the attack.
People are searching for their relatives among the dead bodies
She and her party are observing three days of mourning after which she is expected to visit her father's tomb in the family's ancestral village north-east of Karachi.
The deadly attack on her homecoming procession has cast doubts on her plans to travel around the country generating support.
The government has said the January polls will take place as planned, but officials have suggested that public rallies could be restricted or even banned.
Thursday's attacks on Ms Bhutto's motorcade in Karachi were among the bloodiest Pakistan has ever seen.
In an interview with the BBC, Ms Bhutto said she was lucky to be alive.
"I don't believe the state or the government was involved in the attack on me at this stage," she said.
"But I do believe that the sympathisers of the militants had managed to infiltrate some of our agencies... to give covert support to the militants."
Ms Bhutto says she has sent President Musharraf the names of three former military officials she accuses of involvement in the attack.
Deputy Information Minister Tariq Azim said the authorities had yet to see any evidence.
Mrs Bhutto was travelling from the airport to the Quaid e Azam mausoleum where she was due to address a rally
Her slow moving convoy was attacked near the recently built Karsaz bridge on the Sharah e Faisal, the main road into the city centre
Following the blasts, scores of wounded were taken to the nearby Jinnah medical centre