A suicide bomber on a motorbike struck a joint Afghan-NATO patrol in the town of Khost on Wednesday, killing 17 Afghans and causing coalition casualties, officials said. The blast in the eastern town close to the border with Pakistan, where Taliban and other Islamist insurgents fighting US-led troops have strongholds, also wounded 37 people, hospital officials said. There was no immediate claim of responsibility but interior ministry spokesman Sediq Sediqqi blamed the "enemies of Afghanistan", a phrase commonly used by Afghan officials to refer to the Taliban. The Taliban, leading a 10-year insurgency against President Hamid Karzai's western-backed government, have begun the annual fighting season with a series of attacks which saw US Defense Secretary Leon Panetta admit that violence was rising. Sediqqi said Wednesday's blast was aimed at a combined Afghan and coalition patrol passing through Khost. It is the second significant attack on NATO forces this month in the town, after a suicide truck bomber targeted a US-run base on June 1, sparking clashes that left up to 15 people dead. US media reported that more than 100 American troops were treated for injuries after that blast. Amir Padsha, the director of Khost city hospital said 11 dead had been brought to his hospital, including three police officers and eight civilians, along with 17 wounded. Babri Gul, the head of the Babri Gul private hospital in Khost, said he had received six bodies, including four members of the same family, and 20 wounded. Major Martyn Crighton, a spokesman for the International Security Assistance Force (ISAF) confirmed the attack targeted coalition and Afghan forces. He said it "caused some ISAF casualties", but was unable to say whether the troops were dead or wounded. The bombing came a day after Taliban suicide attackers struck two Afghan-NATO facilities in the southern province of Kandahar -- the birthplace of the extremist movement and the heartland of its insurgency. Seven insurgents stormed a joint Afghan-NATO base in Shah Wali Kot district in the early hours of Tuesday morning and hours later four attackers in Afghan police uniforms struck a police post, killing four officers. Khost is one of the most troubled regions in Afghanistan. It shares a porous border with Pakistan's tribal belt, which lies outside government control, and where US officials say the Taliban and Al-Qaeda have carved out bases for operations in Afghanistan. The Haqqani network, a militant group close to Al-Qaeda and blamed for some of the most daring insurgent attacks in Afghanistan, is particularly active in the border province. The Taliban have waged a bloody fight against Karzai's administration since they were ousted from power in a US-led invasion in 2001. The vast majority of the 130,000-strong NATO force is due hand over security duties to Afghans and leave the country by the end of 2014, and there have been fears over local forces' ability to maintain peace.