He said: "The best way for stability in this part of the world - in Afghanistan and in Pakistan, is an effective, sincere and very serious fight against extremism and terrorism."
"Unless we do that, we will continue to suffer."
Karzai had also said that the six parliamentarians killed in the blasts - who included Mustafa Kazemi, a former commerce minister - would be given a state funeral.
The parliament has suggested that they all be buried near the parliament building as a memorial.
Almost all of the country's television stations abandoned normal programming to broadcast recitations from the Quran, as well as religious music and analysis of Tuesday's attack.
Al Jazeera's Hamish MacDonald, reporting from Kabul, says that confusion still remains as to the exact nature of the attacks and who was responsible.
He said: "The president had suggested that the death toll was 35 as a result of the bombings in Baghlan."
"Since then, another report has emerged suggesting that the death toll could be as high as 41."
According to Zemarai Bashary, the interior ministry spokesman, the head of the counterterrorism and criminal investigation branches were investigating in the town of Pul-i-Khumri, where the blast tore through the delegation of parliamentarians.
|Mustafa Kazemi was among the members|
of parliament killed in Tuesday's blast [AFP]
The Taliban, despite government accusations, has continued to deny any involvement in such attacks.
MacDonald said that the group had gone as far as to condemn the attacks.
There have been about 120 suicide attacks in Afghanistan this year, most of them blamed on the Taliban.
In the area of Baghlan, there are tensions between the mainly ethnic Tajik leadership in the region and remnants of the Hezb-i-Islami group, whose leader Gulbuddin Hekmatyar, an ethnic Pashtun, is sympathetic to Osama bin Laden and al-Qaeda but denies any organisational links.