The US and other nations have started to withdraw some troops from the nearly decade-long Afghan war, saying they have made progress in taming the Taliban insurgency by routing their strongholds in the south.
But the Taliban has hit back with several high-profile attacks in the capital and assassinations of government officials and key senior figures that has raised questions about how solid a grip the Afghan government and its Western allies have on security - and whether the Afghan forces can ever secure the nation by themselves.
In its quarterly report on Afghanistan released Wednesday, the UN said that as of the end of August, the average monthly number of incidents stood at 2108, up 39 percent over the same period a year earlier.
The report also said that while the number of suicide attacks remained steady, insurgents were conducting more complex suicide operations involving multiple bombers and gunmen. It said that on average, three complex attacks have been carried out each month this year - a 50 percent increase compared with the same period last year.
The ambush on the police checkpoint took place near Lashkar Gah, the capital of Helmand province. The city is one of seven areas of Afghanistan where Afghan security forces have started taking over from US-led coalition forces.
Gen. Nabi Jan Mullahkhail, deputy regional commander in the south, said three policemen also were wounded in the pre-dawn attack.
Mullahkhail said a policeman who was manning the checkpoint has gone missing. Authorities are investigating whether he might have been involved in the attack.
A day earlier in Lashkar Gah, a suicide bomber rammed an explosives-packed vehicle into a police truck, killing two civilians. The Taliban claimed responsibility for that attack.
Lashkar Gah was one of five provincial capitals chosen for the first-round transition of security from NATO to Afghan hands this summer. The process also included two provinces.
NATO hopes to use the security zone around the city and the central Helmand River Valley as a foothold to push Afghan governance into outlying areas as coalition forces plan to withdraw combat forces from the country by the end of 2014.
Also in Helmand province, Afghan and US-led coalition troops destroyed drugs worth more than $350 million and three drug laboratories in what is believed to be Afghanistan's largest drug seizure this past decade, NATO said Wednesday.
The money from the drugs was believed to be bankrolling attacks on Afghan and coalition forces.
Acting on intelligence, the troops targeted an area in Helmand's Baghran district on Monday that was suspected of being a manufacturing site for drugs and destroyed more than 12,065kg of chemicals used to make drugs, 100kg of heroin and 80kg of opium. Afghanistan produces about 90 percent of the world's opium.
Separately, a New Zealand special forces soldier was shot in the head and killed during a gunbattle with suspected insurgents in a compound near Afghanistan's capital.
Lt. Gen. Rhys Jones, the chief of New Zealand's defence force, said the soldier was part of a team of 15 supporting about 50 Afghan police trying to serve arrest and search warrants to a group suspected of planning an attack in Kabul.
Jones said a man and a child in the compound were wounded during the battle, which continued for hours.
