He ordered an inquiry and sought a report from Punjab Chief Minister, Shahbaz Sharif.
Punjab Law Minister, Mujtaba Shujaur Rehman claimed that the suicide bomber managed to cross four security checkposts on GT Road.
Two of the four posts had been set up after a threat was reported by the intelligence agencies Sunday morning.
The minister said the target of the bomber was the flag-lowering ceremony.
According to reports of the Punjab home ministry, 10 to 15 kg of explosives were used in the suicide bombing.
Evacuee Trust Property Board chairman Siddiqul Farooq said that the safety of over 2,000 Sikh pilgrims, who are scheduled to arrive in Lahore Tuesday for the three-day birth anniversary celebrations of Guru Nanak, will be ensured, Dawn reported.