Afghan security forces are dying at five times the rate of NATO soldiers as Taliban insurgents step up attacks ahead of the withdrawal of foreign troops in 2014, the latest figures show.

While deaths among NATO's troops are regularly chronicled in the 50 countries that contribute soldiers to the war, the daily casualties among the Afghans they are fighting alongside rarely make headlines.

A total of 853 Afghan soldiers and police were killed in the past four months, government figures show, compared with 165 NATO troops, according to a tally kept by the website icasualties.org.

President Hamid Karzai warned in May that the Afghan death toll would increase as the US-led troops start withdrawing and hand increasing responsibility for security to Afghan forces.

Both NATO's International Security Assistance Force (ISAF) and Afghanistan's interior ministry have noted a surge in attacks in recent months since the start of the Taliban's annual summer offensive.

"Enemy-initiated attacks over the last three months (April-June) are 11 percent higher compared to the same quarter last year," ISAF said in a report last week.

The month of June alone saw the highest number of attacks in nearly two years, with more than 100 assaults a day across the country, including firefights and roadside bombings, the US-led coalition said.

Interior Ministry spokesman Sediq Seddiqi said at the weekend that there had been a surge in casualties suffered by police in the past four months, with 635 killed and 1,246 wounded.

"This year, the enemies of Afghanistan have intensified their attacks against Afghan security forces," he said.

"We have increased our operations against the enemy and they also intensified their attacks," he said, adding that 1,730 insurgents had been killed over the same period.

The upturn comes as NATO countries have already started to withdraw their 130,000 troops after more than 10 years of war and ahead of a 2014 deadline for an end to combat operations.

Politicians in NATO countries, where polls show that most voters want their soldiers out of Afghanistan, regularly refer to "ending the war in 2014".

But all signs point to the fact that the war will not end for the Afghans -- and could get much worse.

"The Taliban are sure that at the end of the day the foreign forces will leave and the only force that will remain to fight them is the Afghan force," author and analyst Waheed Mujda told AFP.

"Since they started their new summer offensive their goal has been to target Afghan forces, to demoralise them and to create fear so that no one could join them," he said.

Mujda also suggested that the government underplayed casualties in their statistics because "they don't want to demoralise the forces".

He said a more realistic figure had been presented earlier this month by a former chief of the National Directorate of Security, Amrullah Saleh, who said more than 1,800 members of the Afghan security forces were killed in the previous three months -- well over double the official figure.

Defence Ministry sources told AFP that in the four months since the start of the Afghan solar year at the end of March, 218 Afghan soldiers had been killed.

Police, who play a paramilitary role in the war-torn country, are more exposed to insurgent attacks in local areas where they are always on the roads or manning small checkposts while the army operates out of fortified bases.

ISAF said one reason for the increase in the number of attacks over recent months was an earlier start to the summer fighting season because of an early end to the harvest of opium poppies -- a major source of income for Taliban Islamist insurgents.

Another was the increased presence on the battlefield of Afghan security forces as they take more responsibility from NATO troops ahead of the drawdown.

Despite the rise in attacks, the number of coalition deaths in the first six months this year -- 220 -- was down on the same period last year when 282 died, according to icasualties.org.

About half of all deaths in both periods were due to roadside bombs, the statistics show.

The homemade bombs are also responsible for most civilian deaths -- which run higher than those for either army.

According to the United Nations, the number of civilians killed in the war has risen steadily in the past five years, reaching a record 3,021 in 2011 -- the vast majority of the deaths caused by insurgents.