Pakistan says US-led coalition forces in Afghanistan have mistakenly killed one of its soldiers at a border post.
Pakistan has tens of thousands of troops in the border area
Two other soldiers were wounded when coalition forces opened fire in the Shawal area of North Waziristan region, a Pakistan military statement said.
It said a "strong protest" had been lodged with the coalition, which said it was investigating the incident.
Earlier, at least three Pakistani security personnel were killed in a roadside bombing in North Waziristan.
The BBC's Haroon Rashid in Peshawar says coalition forces have in the past violated Pakistani air space, but this would be the first time Pakistani troops have been killed.
Early last year US planes bombed three compounds in the Bajaur tribal region, killing at least 13 people. Pakistan protested then too.
The Pakistani military statement said coalition troops had "mistakenly fired on one of our posts near Shawal", a mountainous area near the long and poorly demarcated border with Afghanistan.
"A strong protest has been lodged with the coalition authorities about the incident, asking them to investigate the matter and take necessary steps to ensure that such incidents are not repeated in future," the statement said.
A spokesman for the coalition said it had dropped four bombs on four suspected militants who had fired rockets at US soldiers at Bermel, in Afghanistan's Paktika province - just over the border from North Waziristan.
"I cannot confirm or deny loss or injury of Pakistani military," Lt Col Paul Fitzpatrick, a US military spokesman in Afghanistan, told the Associated Press news agency.
"This all happened inside Afghanistan."
Pakistan has stationed tens of thousands of troops in its volatile tribal areas along the border with Afghanistan as part of its contribution to the US-led "war on terror".
President Pervez Musharraf's decision to support the US has angered many Pakistanis.
The Afghan government, the US, Nato and others say the Taleban and their allies have been using Pakistan's border areas to regroup.
Pakistan, which has been under increasing pressure over cross-border incursions, rejects suggestions it is not doing enough to counter militants opposed to the US-backed government in Kabul.
Earlier on Monday, at least three members of the Pakistani security forces were killed and nine others hurt, some critically, in an apparent suicide attack elsewhere in North Waziristan.
Security forces kept people away from the Miran Shah attack
The military said the bomb hit an army vehicle at the Khajori check post on the outskirts of the region's main town, Miran Shah.
"There was an administrative convoy on the Bannu-Miran Shah road. A white car came near it and exploded. As a result, three security officials were killed and nine injured," military spokesman Shaukat Sultan said.
Controversial peace deals have been reached with pro-Taleban militants in the area.
The militants swiftly denied they were involved in Monday's blast.
No group has said it carried out the attack and our correspondent says it is not clear who was behind it.
Last week, the air force bombed a suspected militant camp in nearby South Waziristan, prompting local pro-Taleban tribal leaders to threaten revenge.