President Hamid Karzai on Sunday accused Pakistan of firing 470 rockets into two eastern Afghan provinces over the past three weeks, a deadly rain of artillery that Afghan officials said killed 36 people, including 12 children.

The attacks came in areas of Kunar and Nangahar provinces where NATO forces have withdrawn, and where Pakistani Taliban moved in behind fleeing civilians, Afghan border officials said.

Karzai indicated Pakistani government forces are responsible for the bombardment, and "they should be stopped immediately." And "if they are not being carried out by Pakistan, Pakistan should make it clear who is behind the attacks," he said in a statement issued by the presidential palace.

Afghan security officials said joint NATO and Afghan border units have fired back into Pakistan, but NATO and Pakistan military officials denied any knowledge of border skirmishes.

NATO reported, meanwhile, that five service members were killed in at least three insurgent attacks in western, southern, and eastern Afghanistan on Sunday. The international coalition gave no other details. The deaths bring to at least 53 the number of NATO service members killed in June, and to more than 200 this year.

Karzai said he discussed the rocket barrage with Pakistani President Asif Ali Zadari during an anti-terrorism conference in Tehran on Saturday, the same day the Afghan Defense Ministry spokesman warned that Afghanistan would defend itself.

"The government of Pakistan should understand that there will be a reaction for killing Afghan citizens," said spokesman Mohammad Zahir Azimi.

The Afghan president said he also discussed the border attack with Afghan NATO commander Gen. David Petraeus and U.S. Ambassador Karl Eikenberry during his regular national security council meeting on Sunday.

American and Afghan officials have pressured Pakistan to end its security forces' long-standing relationship with the Taliban movement, viewed as a tool for Pakistani influence over strategically placed Afghanistan. Such major artillery support for a Taliban operation, however, would be one of the most blatant recent examples of Pakistani support and bodes ill for the testy relationship among the three countries.

Afghan border police spokesman Edris Mohmand, who reported 36 Afghans killed by the rockets, including 12 children, said 2,000 families have fled districts threatened by the barrage, including Asmar and Nangalam in Kunar, and Goshta district in Nangahar.

"All these attacks have been from Pakistan's side and for sure they are Pakistani weapons being used against innocent Afghans," Mohmand said. "The border police in the eastern region have been equipped with heavy artillery but we are waiting for orders from the interior minister."

NATO has recently withdrawn many of its combat troops from forward operating bases and combat outposts in Kunar and Nangarhar. Both provinces continue to be heavily contested by Taliban fighters.

Spokesman Azimi said the Afghan Defense Ministry "asks the president of Pakistan to stop the artillery firing and compensate the losses caused."

Violence has been on the rise across Afghanistan since the country's Taliban Islamists launched a spring offensive and promised retaliation for the death of al-Qaida leader Osama bin Laden in a U.S. raid in Pakistan on May 2.

The deadliest single attack since February occurred on Saturday in eastern Afghanistan, when a suicide bomber blew up his sport utility vehicle at a health clinic while women and children lined up for maternity care and vaccinations. At least 35 were killed.

The vehicle smashed through a wall at the Akbarkhail Public Medical Center before anyone could shoot the driver or blow out the tires, local officials said. The force of the blast caused the building to collapse.

Survivors frantically dug through the rubble with shovels and bare hands. At least 53 other people were wounded, said the provincial public health director, Dr. Mohammad Zaref Nayebkhail.

"They were offering important services for the people. We had very good services and lots of patients. There were only 10 beds but lots of other services in that center. It's why the casualties were so high," he said.

Wary of being blamed for civilian casualties, the Taliban denied it was behind the bombing in Azra district in Logar province.

"This attack was not done by our fighters," Taliban spokesman Zabiullah Mujahid told The Associated Press in a telephone interview.

The Taliban claims it does not target civilians, but the movement is fractured and Saturday's attacks shared characteristics of other recent violence.

A recent U.N. report found that May was the deadliest month for civilians since it began keeping track in 2007, and it said insurgents were to blame for 82 percent of the 368 deaths recorded.