KABUL, Afghanistan (AP) -- In a bloody day for NATO troops in Afghanistan, insurgents killed six service members Wednesday, including four who died in a single bomb blast in the volatile south of the country.
One service member was killed in the east in an attack early in the day, and another died in the south in a separate roadside bombing - the weapon of choice for militants in countering a large-scale NATO-Afghan operation in the region.
NATO did not provide nationalities of the dead, or specific locations where the attacks occurred.
2010 has been the deadliest year for international troops in the nine-year Afghan conflict. At least 34 NATO service members have been killed so far this month. More than 2,000 have died since the 2001 U.S.-led invasion.
Troop numbers have been ramped up in the past year to turn the screws on the insurgents. Fighting has intensified and casualties have mounted. The escalating toll has shaken the commitment of many NATO countries, with calls growing to start drawing down troops quickly.
The nearly 150,000 international troops and 220,000 Afghan government security forces - whose recruitment and training has been put on a fast track - are still struggling to gain the upper hand against an estimated 30,000 insurgents.
NATO's top commander in Afghanistan, Gen. David Petraeus, offered a cautiously optimistic assessment of the transition of security duties to Afghan forces during a briefing with alliance representatives in Brussels on Wednesday.
"There are areas of the country that are reasonably secure already, and Afghan security forces are capable of handling security already," his civilian counterpart, Ambassador Mark Sedwill, told reporters after the session.
The process should be completed by 2014, although some allied troops - including special forces and trainers - will remain in Afghanistan after that date, Sedwill said.
As they seek to turn around the war, which recently entered its 10th year, NATO and Afghan forces are increasingly targeting insurgent leaders.
A commander and three other militants from the Haqqani network - a Pakistan-based faction of the Taliban with close ties to al-Qaida - were killed in a firefight with NATO and Afghan forces in eastern Khost province's Spera district overnight Tuesday, a NATO statement said.
As the security force moved in on a compound, two insurgents threw a grenade and opened fire. Retaliatory fire killed four militants, including the commander, Ansari Khan, it said.
The Haqqani network is most active in eastern Afghanistan and presents one of the greatest threats to foreign forces.
On Monday, a coalition airstrike killed Taliban commander Shirin Agha and another militant in northern Kunduz province, NATO said. Over the past month, the alliance says Afghan and coalition forces have killed or captured 18 Taliban commanders in the north where violence has surged in recent weeks.
It was not possible to verify independently the identities of the slain insurgent commanders.
Taliban spokesman Qari Yousef Ahmadi has accused NATO of a propaganda campaign to demoralize the insurgents by inventing Taliban leaders and alleging they were killed or captured.
In other violence, insurgents fatally shot Ahmed Khan, chief of Dihrawud district in southern Uruzgan province, at a market on Tuesday, according to Mohammad Naeem, the district police chief.
Associated Press writers Heidi Vogt in Kabul and Slobodan Lekic in Brussels contributed to this report.