Pakistan has vowed to track down the leader of a kidnap group in South Waziristan after one of two Chinese hostages died in a rescue attempt.
Wang Ende meets Pakistan minister Liaquat Jatoi after being freed
Pakistani forces launched the mission on Thursday, killing five kidnappers who had abducted the Chinese engineers last weekend.
Kidnap leader Abdullah Mehsud directed the kidnapping from another location.
Chinese Prime Minister Wen Jiabao has asked Pakistan to ensure the safety of Chinese citizens in the country.
President Pervez Musharraf sent a message to Chinese President Hu Jintao after the rescue mission, saying the "masterminds behind this terrorist action will be pursued relentlessly and meted out the most severe punishment".
On Friday a Pakistani government official said "all possible measures" were being used to track Mehsud down.
A security official told the Reuters news agency: "We have to hunt [Mehsud] down. Now we will evolve a strategy
and do some planning. The man has become too big for his shoes."
Mehsud was freed in March after 25 months in US custody in Guantanamo Bay in Cuba. There is no word on his whereabouts now.
He had refused to hand over the Chinese until safe passage had been granted for his men.
Security forces began their rescue after hearing shots from inside the surrounded mud compound near Chagmalai, in the Afghan border region.
The hostages had been handcuffed and their legs chained. They were also strapped with explosives.
Wang Peng was killed but his colleague Wang Ende was returned safely to Chinese diplomats.
A Pakistani guard and a soldier who were also taken captive had been released earlier.
A delegation sent from the Mehsud tribe to Abdullah Mehsud had earlier failed to secure any releases.
Mehsud kept a high profile during the kidnapping.
The BBC's Rahimullah Yusufzai met him shortly before the end of the siege and was even allowed to speak to the kidnappers by telephone.
Our correspondent says Mehsud appeared uncompromising and emotional but also careless with communications.
This is the second time in recent months that Chinese engineers have been targeted in Pakistan.
In May, three were killed by a car bomb in the south-west of the country.
The blast occurred as the engineers were being taken to work on a project developing port facilities in the city of Gwadar, near the border with Iran.
Now Chinese Prime Minister Wen Jiabao, has asked his Pakistani counterpart, Shaukat Aziz, to take "effective measures" to protect Chinese citizens working there.
'Through the window'
In June, another tribal leader who challenged the Pakistani military, Nek Mohammed, was killed by a missile fired at his home after he was tracked by satellite phone communications.
One diplomat told the Reuters news agency: "I've a feeling Abdullah will soon get a missile through his window just like Nek Mohammad."
Mehsud tribal members condemned the kidnapping of the Chinese.
National Assembly member, Maulana Mirajuddin Khan, said: "The [kidnappers] have disgraced the movement against US influence in the region."
Diplomats say Pakistan will be eager to bring to justice a man who has embarrassed relations with one of its closest allies.