President Obama's war cabinet discussed the arrest on Wednesday
The US has hailed the capture of the Afghan Taliban military commander, Mullah Abdul Ghani Baradar, as a "big success" for US-Pakistani cooperation.
A White House spokesman confirmed the capture for the first time, saying it was a significant development.
Pakistan earlier confirmed the capture which was reported on Tuesday.
Interior Minister Rehman Malik added that other suspects had been arrested in the swoop "seven to 10 days ago" and were being interrogated.
Mullah Abdul Ghani Baradar is said to have overseen Taliban military operations in Afghanistan, run the group's leadership council, and controlled its finances.
White House spokesman Robert Gibbs said the detention was a significant development for joint US-Pakistani efforts to combat Islamist extremists.
Rehman Malik denied US agents had been involved in the capture
But he did not say if the detainee was providing any intelligence.
The Taliban say Mullah Baradar, thought to be their second-in-command, is still free and is in Afghanistan.
American officials had said on Tuesday that Mullah Baradar was seized by US and Pakistani agents in Karachi on 8 February.
But Mr Malik "categorically" denied US agents had taken part.
"Nothing of the sort has happened. The operation was carried out by Pakistani security agencies."
He said only Pakistani agencies were involved in the interrogation, but added: "Yes, there is a sharing of intelligence because we are fighting the war together."
Mr Malik described the capture of a man "very close to [Taliban leader] Mullah Omar" as "a big catch for Pakistan".
"It's a serious setback for them. He is a main military commander," he said.
"Others were also arrested and are being interrogated. But it's too early to say anything about them. We will disclose details when the time comes."
The interior minister said the operation showed "how sincere and serious we are on the war on terror".
A separate operation on the Afghan border had led to several further arrests and the seizure of a number of suicide bomb jackets and landmines, he said.
The news of Mullah Baradar's arrest came as Nato forces and Afghan troops are conducting a major offensive against the Taliban in Afghanistan's southern Helmand province, an area he is believed to have been responsible for.
His influence within the Taliban is said to be second only to that of Mullah Omar, who has been hiding from Western agencies since the 9/11 terror attacks of 2001.
His capture was discussed at a meeting of Barack Obama's war cabinet on Wednesday, at which the US president was briefed on the progress of Operation Moshtarak.
The arrest suggests Pakistan is getting tough with Afghan Taliban leaders sheltering there, says the BBC's Orla Guerin in Islamabad, something that has long been a demand of the White House.
The arrest could also put pressure on other Taliban leaders to enter into talks with the Afghan government and coalition forces, something Mullah Baradar is believed to favour, our correspondent says.
Afghan and Nato leaders have said reconciliation talks with more moderate Taliban members could be pursued to end the insurgency.
Meanwhile, missiles fired by a suspected US drone aircraft have killed at least three militants in north-west Pakistan, security officials say.
The attack targeted a compound in Tapi Tolkhel village, 15km (9.3 miles) east of Miranshah, the main town in North Waziristan, by the Afghan border.
The regions of North and South Waziristan are known sanctuaries for al-Qaeda and Taliban militants who move easily across the mountainous border into Afghanistan.
They are frequently targeted by drone attacks and there have been more than a dozen such strikes in 2010.