Officials with the international forces in Afghanistan say militants have killed eight U.S. troops and five Afghan civilians in separate incidents since late Tuesday.
NATO officials say four U.S. soldiers were killed in a roadside bombing in southern Afghanistan, while one American service member was killed in a separate gunbattle.
Officials also said militants attacked an Afghan police headquarters in Kandahar city late Tuesday, killing three American soldiers and five Afghan civilians, including translators.
Lieutenant Commander Katie Kendrick is a spokeswoman for the international forces. She described the attack to VOA by phone.
"Insurgents attacked the headquarters in a vehicle-borne improvised explosive device joined by small arms, rocket-propelled grenades and machine-gun fire. Afghan National Civil Order Police and international forces secured the headquarters and prevented insurgents from penetrating the compound," she said.
The Taliban claimed responsibility for Tuesday's assault.
The American deaths bring the number of international forces killed in 24 hours to 12, making it one of the deadliest days for NATO in Afghanistan.
Amrullah Aman is a retired Afghan general. He tells VOA he thinks the Taliban could be capitalizing on apparent rifts within the international community and with the Afghan government.
He says that he believes the Taliban has shown better coordination than the international community and the Afghan government, especially during the past two months.
The top military commander in Afghanistan, U.S. General David Petraeus, recently assumed command following a controversy surrounding his predecessor, General Stanley McChrystal.
In addition, the Afghan government continues to face accusations of corruption, despite pledges by President Hamid Karzai to combat it.
Retired General Aman says he does not think the Taliban is strong. He points out that they lack heavy weapons, planes and even what he terms good logistical support. He just thinks the international community should further strengthen the Afghan forces.
June was the deadliest month for international forces in the country with more than 100 service members killed.
The Taliban has increased attacks as NATO and Afghan forces intensify their fight against militant strongholds in the south.