KABUL - Taliban-style bomb attacks killed five US soldiers in Afghanistan Saturday, NATO said, as the death toll of foreign soldiers in the nine-year Afghan war climbed towards the 2,000 mark.

NATO`s International Security Assistance Force (ISAF) said the five had died in two separate attacks involving improvised explosive devices, or IEDs, the main weapon deployed by the Taliban in their insurgency.

An ISAF spokeswoman confirmed all five were Americans.

An incident early in the day claimed the lives of four of the American soldiers, while the fifth was killed later Saturday, according to ISAF statements.

Both attacks took place in southern Afghanistan, where the war is at its fiercest, ISAF said.

The deaths bring to 397 the toll of foreign soldiers killed in the war so far this year, compared with 520 for all of 2009.

An AFP tally based on that kept by the icasualties.org website puts the number of soldiers to have died since the Afghan insurgency began in 2001 at 1,965, with 1,205 of them Americans.

IEDs are the main cause of foreign soldiers` deaths, according to military officials, who say the payload of the crude home-made bombs is rising as the Taliban insurgents adapt to the greater defences of the foreign forces.

The US and NATO have almost 150,000 troops in Afghanistan, with the surge of an extra 30,000 Americans ordered by US President Barack Obama almost fully deployed, most of them in the southern hotspots of Kandahar and Helmand.

Obama has said he wishes to start drawing down US forces in the middle of next year, and Britain, which has the second largest combat contingent in the country, is eager to pull out within five years.

Afghanistan`s army and police are being trained by their international counterparts, with plans to reach a combined force of 300,000 by later this year, aiming for a deadline for taking over security of 2014.

President Hamid Karzai`s pledge made at his inauguration speech in November, when he began his second term as president, was reiterated at a conference in Kabul this week of his international supporters.

His promise that Afghan security forces would be competent enough to work alone to secure the country from the Taliban onslaught has been met with some scepticism that numbers are more important than the ability to meet targets.

Washington`s top military officer, Admiral Mike Mullen, arrived in Islamabad Saturday amid US concerns about sanctuaries in Pakistan for extremist groups blamed for attacks on Afghan targets.

Speaking to reporters in New Delhi before leaving for Islamabad, Mullen described the Haqqani network, believed to be based in Pakistan`s North Waziristan tribal district, as "the most lethal network" faced by US-led coalition in Afghanistan.

Pakistan has long faced charges that it provides safe havens for groups such as the Haqqani, which fund, staff, plan and carry out attacks in Afghanistan.

The Afghan government has called on Pakistan to take action against the groups, which it has said operate with impunity from Pakistani soil, with the tacit support of the state intelligence agency and elements of the military.

Two US lawmakers -- Democrat Dennis Kucinich and Republic Ron Paul -- this week proposed a bill calling for the withdrawal of US troops from Pakistan, where they said they were conducting covert operations against militant groups.

"We have known that US forces have been operating in secret inside the territories of Pakistan without congressional approval," Kucinich said Friday, pointing to reports the United States was stepping up its presence there.

The Pentagon says only that a small number of US soldiers operate in Pakistan, mostly Special Forces tasked with training Pakistani troops along the Afghan border.

The Taliban earlier this year promised to step up attacks not only on foreign and Afghan military, but against anyone associated with the government.

With parliamentary elections set for September 18 as the next step in the so-called "Kabul process" of national development, violence against parliamentary candidates appears to be the Taliban`s next tactic.

Candidate Sayedullah Sayed, who was wounded when the mosque where he was holding a campaign event in the eastern province of Khost on Friday was bombed, had died of his injuries, officials said.

BDST: 1800 HRS, July 24, 2010