Now, the northern supply line hit: 22 NATO trucks bombed

The Taliban said they detonated a bomb on a fuel tanker Wednesday and then opened fire on other NATO supply trucks in a morning attack that destroyed 22 vehicles loaded with fuel and other goods for US-led coalition forces in Afghanistan.

Elsewhere in the country, two NATO service members were killed in a roadside bombing Wednesday in the east, while another died Tuesday in an insurgent attack in the south. A NATO helicopter crashed in the west, injuring two other service members. And Afghan officials said nine Afghan soldiers died Tuesday night when militants attacked a checkpoint in in the south.

Violence continues across Afghanistan at a time when its own forces are taking charge of security in more areas as foreign troops continue to withdraw. The US-led coalition is confident that Afghan forces will be ready to take responsibility for the entire nation's security by the end of 2014 when international combat forces will have gone home or moved into support roles.

To show they remain a resilient force, insurgents are conducting targeted attacks – even in relatively peaceful parts of the nation like Samangan province in the north.

The Taliban said they attacked NATO supply trucks parked overnight in the Rabatak area of Samangan.

"We put explosives on a fuel tanker. When it exploded, we fired on the trucks," Taliban spokesman Zabiullah Mujahid told The Associated Press in a telephone call.

Sidiq Azizi, a spokesman for the province, said many tankers and semi-trailers caught fire after the bomb went off around 2 a.m.

By mid-day, heavy black smoke still poured from the area where the truckers had stopped to rest. Firefighters were spraying water on the burning vehicles.

"There was a big boom," Azizi said. "It's possible that is was a magnetic bomb from insurgents. We are investigating."

"I counted 20 fuel tankers burning. There is still a very big fire," said Azizi, who was at the scene. "The weather is very hot and it's hard to get close to the fire."

The tankers in the convoy were transporting fuel south toward the Afghan capital, Kabul, from neighboring Uzbekistan to the north.

Earlier this week, three NATO supply trucks were destroyed by militants in Sayd Abad district of Wardak province in eastern Afghanistan.

Convoy traffic in the east has gotten heavier since Pakistan reopened its border crossings about two weeks ago. Islamabad blocked NATO supply trucks for seven months in retaliation for US airstrikes that killed 24 Pakistani soldiers.

NATO said the helicopter crashed early Wednesday in an undisclosed location in the relatively peaceful western Afghanistan. No other information has been released about the crash, which is under investigation. The extent of the two NATO service members' injuries was not disclosed.

The Helmand provincial governor's office said the Afghan soldiers died when armed militants attacked an Afghan National Army checkpoint in Washer district. Seven insurgents were killed in the attack, the governor's office said. Insurgents also clashed Tuesday night with Afghan police in Nad Ali district. An insurgent commander was killed and six other militants were captured during the battle, the governor's office said.

Insurgents are trying to regain territory they lost during the past two years when tens of thousands of US, NATO, and Afghan forces routed them from their strongholds in the south.

So far this year, 240 coalition service members have been killed in Afghanistan, including at least 172 Americans.

* Associated Press Writer Deb Riechmann in Kabul contributed to this report.