Kabul, Afghanistan (CNN) -- Afghans in government uniforms launched three attacks on U.S. and Afghan forces in a 24-hour period, including one that breached the perimeter of an American outpost near Kandahar, a Pentagon spokesman said Tuesday.
The strikes made for what Capt. John Kirby, a Pentagon spokesman, called a "tough day" around the southern city of Kandahar. A U.S. soldier was killed and several others were wounded in a shooting by gunmen in Afghan police uniforms Monday, and other disguised insurgents killed three Afghan police officers and wounded seven more in Kandahar, local authorities said Tuesday.
The most recent attack wounded nine coalition troops at the American outpost dubbed Forward Operating Base Frontenac, in the Arghandab River valley, north of Kandahar. Kirby told reporters Tuesday that the attackers were dressed in the uniforms of the Afghan National Security Forces.
The attackers "were engaged very quickly by friendly forces inside," he said. "There as a quick response force from a nearby combat outpost that responded almost immediately, and most of the casualties were evacuated to Kandahar."
Two U.S. officials, speaking on condition of anonymity, said at least eight insurgents carried out the attack. Seven of them were killed and the sole survivor was wounded, they said.
The area has been the scene of extensive insurgent activity in recent years. Neither official could explain how the breach occurred, but initial reports indicate officials believe the insurgents might have had help from Afghan security personnel.
Uniformed Afghans -- either insurgents in disguise or members of the country's police or military -- have been behind numerous killings of U.S. and NATO troops this year. The incidents have fueled mutual distrust between Afghan and allied forces in the now-decade-old conflict.
Tuesday's clash followed an incident Monday in which three gunmen in Afghan police uniforms fired on American troops in another location in southern Afghanistan, killing one and wounding several others. Kirby said that incident "appears to be what we consider a green-on-blue, an insider threat attack." U.S. forces launched a manhunt for the attackers late Monday, but they remained at large, he said.
And a gun battle erupted at a Kandahar police station early Tuesday morning when four insurgents wearing police uniforms tried to enter the facility, according to the office of the Kandahar governor. Police officers confronted them and a gun battle ensued, leaving the four attackers dead, the governor's office said.
All three strikes were located around Kandahar, the birthplace of the Taliban militia that once ruled most of Afghanistan. But beyond geography, "It's just too soon to say with any certainty the degree to which any of these are connected," Kirby said.
CNN's Barbara Starr at the Pentagon and Masoud Popalzai in Kabul contributed to this report.