Karzai was giving a speech on Sunday to elders and residents in Andar district in central Afghanistan when rockets were fired nearby, said Ali Shah Ahmadzai, the provincial police chief. The rockets missed their target, and no one was hurt.
"After the rockets were fired, we launched a search operation in the area," Interior Ministry spokesman Zemeri Bashary said Monday. "We arrested seven people from nearby villages."
He provided no further details.
Tom Koenigs, the top U.N. official in Afghanistan, said the world body condemned the rocket attack Sunday in central Ghazni province, which narrowly missed Karzai.
"This is an outrage," Koenigs told a news conference. "Those who are responsible clearly do not respect the views of the millions of Afghans who elected President Karzai."
Witnesses said they heard between three and six rockets, but the Taliban claimed it fired 12.
The rockets missed their target, with two of them landing some 200 yards away from the crowd, said Arif Yaqoubi, a local reporter attending the event.
"Please sit down," Karzai told a nervous crowd under a tent in a school yard. "Don't be scared. Nothing is happening."
Karzai finished his speech and his security detail whisked him off by helicopter to Kabul, witnesses and officials said. It was the third attempt on Karzai's life since he became president following the ouster of the Taliban regime in 2001.
Purported Taliban spokesman Qari Yousef Ahmadi told The Associated Press that Taliban militants were behind the attack.
"The Taliban knew that Karzai was coming to Andar district. When Karzai was meeting with the people, the Taliban fired 12 rockets," Ahmadi said by satellite phone from an undisclosed location. "The rockets fell nearby."
Elsewhere, in eastern Khost province, a suicide car bomber blew himself up Monday as police were approaching to search his vehicle at a checkpoint in Gurbuz district, said provincial governor Arsalah Jamal. Eleven people were wounded.
Afghanistan's eastern border provinces have been plagued by insurgency related violence, which has killed about 2,200 people so far this year, most of them militants, according to an AP tally based on reports from western and Afghan officials.
In Kabul, the former head of Afghanistan's radio and television department under the Taliban regime joined the government during a ceremony organized by Ministry of Information and Culture.
Mohammad Ishaq Nezamy, who until recently lived in Peshawar, Pakistan, praised Afghan government efforts at co-opting former Taliban and their sympathizers during a brief speech on Sunday.
"Now it is up to the Afghan people that they should start negotiations with each other and find solutions for their problems," Nezamy said.