Two grenades exploded inside a mosque compound during morning prayers in eastern Afghanistan on Wednesday, wounding at least nine worshippers, an Afghan official said.
The attack in eastern Khost province came a day after a series of bombs around Afghanistan killed 46 people in the deadliest day for civilians this year as Taliban insurgents and their allies ramp up violence across the country.
The Taliban summer offensive this year coincides with Afghan police and soldiers taking on more responsibility for security while international forces start to withdraw.
Three grenades were thrown into the mosque compound in Baghi Sara area, Khost police chief Sardar Mohammad Zazai said. One exploded inside the mosque itself, and one in the courtyard outside. The third failed to detonate.
Zazai blamed Taliban insurgents for the attack.
"This was the work of the enemy," he said. "It cannot be a private dispute. Why would anyone be so angry to throw grenades in a mosque while people are praying?"
He said many of those praying were Afghans who work at the nearby U.S. base, Forward Operating Base Salerno.
Taliban spokesman Zabiullah Mujahid issued a statement that did not acknowledge the mosque attack but claimed an insurgent suicide bomber had attacked a U.S. base in Khost, causing several American casualties.
A spokesman for the NATO military coalition said Wednesday that there was no attack on the Salerno base, which is close to the mosque in Baghi Sara.
Lt. Col. Hagen Messer said the American personnel at the base reported hearing gunfire from the mosque but Afghan police were investigating.
The latest violence comes after a particularly bloody day for Afghanistan.
Suicide bombers launched multiple attacks in a remote corner of southwestern Afghanistan near the Iranian border on Tuesday, killing dozens of people, including shoppers buying sweets for a Muslim holiday.
The bombings left charred and smoldering bits of cookies and dried fruit among the bodies on the ground.
A separate market bombing later Tuesday, this one in northern Afghanistan, brought the overall death toll to 46, most of whom were civilians.
The attacks in provinces on opposite ends of the country Nimroz in the southwest and Kunduz in the north came as the Taliban and their allies step up their assaults in a display of force that often results in civilian carnage.
Militants are especially trying to weaken the still-developing Afghan security forces, who are to assume control across their homeland in 28 months when most foreign combat troops will have left.
The Taliban "want to expand their influence â€" show that they are everywhere," said Afghan political analyst Jawid Kohistani.
"They want to show that the Afghan police are not strong enough so they are targeting the security forces and the government."
Altogether, at least 35 civilians were killed in the attacks in the two provinces, making Tuesday the deadliest day for Afghan civilians this year. The remaining victims were Afghan policemen.
"What we saw today were further acts of intentional mass murder," said Gen. John Allen, the top commander of U.S. and NATO forces in Afghanistan said Tuesday.
"By targeting innocent civilians in populated areas, the insurgents have again shown they will kill non-combatants without hesitation to advance their backward-looking plans for Afghanistan. Once again, I call on (Afghan Taliban leader) Mullah Omar to rein in his murderers. His intentions not to target civilians are hollow," Allen said in a statement.
In past statements, Omar has asked his fighters to avoid civilian casualties. In one message in 2010, for instance, he said: "Pay attention to the life and property of the civilians so that ... your jihad activities will not become a cause for destruction of property and loss of life of people."
The UN reported last week that civilian deaths were lower in the first six months of 2012 than in the first half of 2011, but that an onslaught of summer attacks from insurgents were threatening to reverse that trend.
In all, 1,145 civilians were killed in Afghanistan between January and June of this year, according to the UN report.