Pakistan's President Pervez Musharraf says the killing of a suspected key al-Qaeda militant in southern Pakistan is a serious blow against terrorism.
Amjad Farooqi (alias Hussain) was one of Pakistan's most wanted men
Amjad Farooqi was killed by security forces in a two-hour gun battle in Nawabshah, in Sindh province on Sunday.
"We've eliminated one of the very major sources of terrorist threat," President Musharraf said.
Farooqi was wanted in connection with attempts to kill the president and the murder of US reporter Daniel Pearl.
At least three men were killed in the shoot-out in Nawabshah, Pakistani officials said.
President Musharraf said on his trip to the Netherlands on Monday: "Not only was [Farooqi] involved in the attacks on me but also in attacks elsewhere in the country. So a very big terrorist has been eliminated."
President Musharraf said intelligence reports suggested al-Qaeda leader Osama Bin Laden was alive, but he did not know where he was hiding.
Senior interior ministry official, Brigadier Javed Cheema, said more suspected Islamic militants were arrested around the country on Monday, including in the city of Sukkar, in Sindh province.
A Sukkar police official said Khalid Ansari, known for links with the outlawed Jaish-e-Mohammed militant group, was arrested there.
Meanwhile, the US commander of coalition forces in Afghanistan said top al-Qaeda figures were more likely to be in Pakistan than Afghanistan.
Lieutenant-General David Barno told Reuters: "We see relatively little evidence of senior al-Qaeda personality figures being here because they can feel more protected by their foreign fighters in remote areas inside Pakistan."
The killing of Farooqi also sparked a security clampdown in Karachi, with consulates, government offices and mosques protected in the face of possible retaliatory attacks.
The BBC's Paul Anderson in Islamabad says that for the Pakistani authorities, all roads to al-Qaeda activities in their country led to Amjad Farooqi.
Our correspondent says he was accused of planning and providing foot-soldiers for several operations bankrolled by the network, including two attempts to assassinate President Musharraf.
"Farooqi's elimination is a crushing blow to the al-Qaeda network in Pakistan because he was the man who had been providing al-Qaeda terrorists with the manpower to carry out attacks," a senior security official told the AFP news agency.
Interior Minister Aftab Ahmed Khan Sherpao told AP news agency that three Pakistani men held at the same time were "possibly involved in terrorist activities inside the country".
"We can't confirm their identities yet," he said.
Mr Sherpao said DNA tests were under way to establish Farooqi's identity beyond question, but Pakistani officials say they are sure they got their man.
Amjad Farooqi, also known as Amjad Hussain, had a 20 million rupee ($330,000) price on his head.
Mr Sherpao said Farooqi had been "incessantly monitored" and was finally trapped at Nawabshah.
"When encircled, he tried to use women and children as human shields. He was killed when he tried to charge the law enforcing agencies with grenades."
Another official said one of the gunmen killed said he would prefer death to arrest and had pointed to the sky, shouting: "I fulfilled my promise to Allah."
Chief Karachi police investigator, Fayyaz Leghari, said a mobile phone call intercepted by intelligence agencies
this month led them to Farooqi's new hideout.
A "big terrorist" has been eliminated, says Musharraf
Zainul Abideen, a man living on the same street as Farooqi in Nawabshah, said: "He is the same man whose pictures we saw today in the newspapers."
Security officials described Farooqi as an "extremely intelligent and elusive terrorist operative," who had set up militant cells which worked independently from each other.
He was said to be a close associate of Abu Faraj al-Libbi, described as the operational chief of al-Qaeda in the region, who is also wanted in connection with assassination attempts on President Musharraf.
The president was unhurt in the attacks on 14 and 25 December last year.
Farooqi was also indicted for involvement in the kidnapping in 2002 and subsequent beheading of Wall Street Journal reporter Daniel Pearl.
Authorities say the killing of Farooqi is the latest in a series of breakthroughs against al-Qaeda in Pakistan.
The government says it has detained more than 70 terror suspects since July, when an alleged al-Qaeda computer expert
and a Tanzanian wanted for east African embassy bombings in 1998 were held.