Afghan security forces were killed at a “shockingly high” rate during what historically has been a winter lull in fighting against the Taliban, a US watchdog said in a report Monday.

According to the US government's Special Inspector General for Afghanistan Reconstruction (SIGAR), 807 troops from the Afghan National Defense and Security Forces died between January 1 and February 24.

“Afghanistan remains in the grip of a deadly war. Casualties suffered by (ANDSF) in the fight against the Taliban and other insurgents continue to be shockingly high,” the report noted.

Levels of violence have traditionally dipped over Afghanistan's cold winter months, but this year the Taliban continued to battle government forces, most successfully in a horrific April 19 attack on a military base outside the northern city of Mazar-i-Sharif.

The massacre saw insurgents armed with guns and suicide bombs slaughter at least 144 recruits, a US official told AFP, though multiple sources have claimed the toll was higher still.

The Afghan Taliban launched their “spring offensive” Friday, heralding fresh fighting the group said would include “conventional attacks, guerrilla warfare, complex martyrdom attacks (and) insider attacks.” Afghan police and army units in 2015 took over from Nato the task of providing security for the country.

According to SIGAR, 6,785 Afghan soldiers and police officers were killed between January 1 and November 12, 2016, with another 11,777 wounded.

The Afghan government has not provided US Forces-Afghanistan with data for the last seven weeks of that year, but even the partial numbers showed an increase of about 35 percent from all of 2015, when some 5,000 security forces were killed.

The SIGAR report also found that both Afghan government and insurgent groups slightly increased the amount of territory they held, as the number of areas previously considered “contested” dropped.

Afghan forces now control 59.7 percent of the country, up from 57.2 percent the previous quarter.

The Taliban and other insurgent groups meanwhile saw their areas of control or influence increase slightly from about 10 percent to 11.1 percent.

The US Congress created SIGAR to provide oversight into how the more than $100 billion appropriated for Afghan reconstruction has been spent since 2002.

Part of its remit is to compile quarterly reports providing snapshots of the country's progress ─ or lack thereof ─ and highlight ongoing challenges to the security situation.

The SIGAR report also points to a UN tally showing that civilian casualties in 2016 were the highest since the United Nations Assistance Mission in Afghanistan began recording them in 2009.

That count found conflict-related civilian casualties in Afghanistan rose to 11,418 in 2016, including 3,498 killed and 7,920 wounded.