Islamabad, Pakistan (CNN) -- A suicide bomber struck Thursday morning outside the gates of a court compound in the heavily guarded administrative heart of the Pakistani city of Peshawar.
At least 19 people were killed and 50 wounded in the attack in the northwestern city, said Dr. Abdul Hamid Afridi, chief executive of Lady Reading Hospital in Peshawar. Four police officers are among the dead, he said.
The bomber stepped out of a taxi near the gates to the Judicial Complex about 10 a.m. Officers on duty grew suspicious as the bomber walked toward the gates, said Nisar Ali Murrawat, a senior officer of the Peshawar police.
When an officer tried to restrain the man by embracing him, the attacker self-detonated what police estimate were 15 kilograms (33 pounds) of explosives, Murrawat said.
The attack was the seventh deadly explosion to erupt in and around Peshawar in less than two weeks.
A wave of suicide bombers has targeted police checkpoints, police stations and the provincial headquarters of Pakistan's spy agency this month, killing dozens of people.
Thursday's blast took place at a time when the judicial compound is normally crowded with lawyers, administrative personnel and the public.
The Judicial Complex is on Peshawar's Khyber Road, across the street from the Pearl Continental Hotel, which was targeted in a deadly bomb attack in June.
At any one time, there are at least three police and military police checkpoints protecting Khyber Road, partly because the provincial Supreme Court, the provincial legislature and Pakistani military offices are nearby.
Taliban commanders have claimed responsibility for several of this month's deadly suicide attacks, including a strike on the intelligence headquarters in Peshawar and a car bombing that killed an area mayor who led an anti-Taliban militia.
Last weekend, the spokesman for the Pakistani Taliban threatened to intensify attacks against Pakistani security forces in a video statement released online.
The Taliban appears to be retaliating for an ongoing Pakistani military offensive launched last month against militant strongholds in the mountainous region of South Waziristan, along Pakistan's border with Afghanistan.
As Pakistani troops and militants fight fierce battles in South Waziristan, drone attacks against suspected Taliban targets continue.
An attack in North Waziristan late Wednesday night killed four people and wounded six others, a Pakistani intelligence official and a local official said.
The U.S. military, which has a presence in neighboring Afghanistan, is the only force in the region able to launch missiles from drones, which are controlled remotely.
CNN's Samson Desta and journalists Nazar Ul Islam and Nasir Dawa contributed to this report.