In the last three weeks more than 100 people, most of them innocent bystanders, have died in six suicide attacks. The government, NATO and a top US official say the apparent new tactic is proof the militants are running scared.

But not everyone agrees.

On Monday, a suicide attack killed 31 people at a government office in the north, while on Saturday the troubled country witnessed its deadliest attack since June when 38 died at a bank in Jalalabad, eastern Afghanistan.

The capital Kabul has also been hit with high-profile attacks, including on a supermarket popular with Westerners and a shopping mall, leading to security on the streets being stepped up in recent days.

Experts say going after such "soft" targets signals a change from the past few months, when the Taliban focused its campaign on roadside bombs, fire fights with foreign troops and some suicide bombings on security targets.

Government officials insist the change is a sign of military progress against the Taliban in the wake of US President Barack Obama's surge strategy.

"A change of tactic is very obvious," said Zemarai Bashary, a spokesman for the interior ministry.

"Since they cannot be successful targeting military institutions... they resort to attacks on civilian targets, soft targets."

Bashary insisted that the number of non-suicide attacks countrywide had meanwhile decreased.

The US Ambassador to Kabul, Karl Eikenberry, said the "terrorist attacks in a way represent gains that we're making in our classic counter-insurgency operations out in the field".

But other experts argue that the Islamists could be "baring their teeth" as a warning ahead of expected offensives by international forces in the spring.

The Taliban, frequently shy of admitting to killing civilians, denied it was now focusing on citizens.

The rebels' spokesman Zabihullah Mujahid said the recent peak in activity was related to better weather, which allowed its fighters to operate more freely following winter snow.

"Our country has been invaded and we do all we can to keep attacking the enemy," he told AFP.

The NATO-led International Security Assistance Force (ISAF) is due to start limited withdrawals in safer parts of Afghanistan in July ahead of an expected transition to Afghan-led security in 2014, allowing most foreign troops to return home.

Tens of thousands of NATO and Afghan security forces pushed into Taliban heartlands in southern Afghanistan in major operations during 2010, nine years after a US-led invasion ousted the Taliban from power.

Military commanders say the hunt will continue this year to completely root out the rebels from safe havens.

"The insurgency obviously tends now to target soft targets, in other words civilians," ISAF spokesman Brigadier General Josef Blotz said.

He added that such tactics were "a kind of weakness of an enemy who obviously cannot confront the Afghan national security forces and ISAF".

Haroun Mir, an analyst with Afghanistan's Centre for Research and Policy Studies, said the recent violence represented a show of strength by the Islamic rebels ahead of a planned spring offensive.

"The Taliban are maybe baring their teeth," he told AFP. "Over the last several months we haven't had any major attacks in Kabul. These days all of a sudden we see an increase."

But he said the nature and location of attacks may indicate the involvement of insurgents other than the Taliban, such as the militant Haqqani network and Al-Qaeda members believed to be based in neighbouring Pakistan.

"The Quetta shura Taliban have less access to Kabul, in fact most attacks in Kabul have been by the Haqqani network who are closer (in the east)," he added.

Others said the change in tactics towards high-impact attacks could be a way for the Taliban to try and increase recruitment ahead of the fighting season, which is expected to start in earnest around April or May.

Another analyst, Waheed Mujda, said the attacks were part of a Taliban strategy to "keep the idea of war alive as they would need to come back after winter and recruit new fighters for their spring campaign."