"An assailant stabbed two Israeli civilians after they had entered Azzun in order to receive medical treatment," the army said, referring to a village east of Qalqilya in the north of the territory.
"Security forces are operating to apprehend the assailant" in a suspected "terror attack", the army said.
Ambulance service Magen David Adom reported late on Saturday morning that its medics had treated a 60-year-old man and his 17-year-old son after they were stabbed near Azzun.
According to Israeli media reports, the two had been visiting a dentist in Azzun and were leaving when a suspected Palestinian youth approached and allegedly asked them if they were Jews before stabbing them.
The reports said the dentist gave them first aid.
The father was lightly wounded in his hand, and the son, stabbed in the back, was in a stable condition, according to medics.
Palestinians sporadically attack Israeli settlers in the West Bank, occupied by Israel since the Six-Day War of 1967, mostly in stabbings and car rammings.
There have been concerns about a possible increase in violence in the run-up to Israel's September 17 general election.
Israel routinely destroys the homes of the families of alleged Palestinian attackers as a form of collective punishment against the community.
The Israeli authorities contend that these punitive demolitions issue "a severe message of deterrence to terrorists and their accomplices – that they will pay a price if they continue their terrorist activities and harm innocent people".
Despite having halted the practice in 2005 after deeming it ineffective, it was reinstated in 2014.
The UN and human rights organisations have said that the practice contravenes international law. However, Israel shows no sign of stopping.
Around 600,000 Israelis live in settlements in the West Bank and annexed east Jerusalem, next to some three million Palestinians.
Netanyahu pledged in April to annex settlements in the West Bank, a deeply controversial move.
Palestinians and many governments around the world warn that continued settlement construction by Israel in the West Bank is eating away at hopes for a two-state solution to the conflict.
Annexing them on a large scale spell the end of such a solution.
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