Kabul, Afghanistan (CNN) -- Dozens of people were killed Wednesday in a series of attacks in Afghanistan as suicide bombers targeted a busy market, an overnight NATO airstrike left 18 dead and militants shot down a U.S. helicopter.
The suicide attack on a market in Kandahar, in southern Afghanistan, killed 22 people and injured 50, President Hamid Karzai's office said.
Karzai, who is on a visit to China, condemned the attacks.
According to Abdul Razaq, a provincial police chief, an initial bomber on a motorcycle detonated his explosives near a restaurant in the market. The market was crowded with civilians and truck drivers, most of them transporting NATO supplies.
When residents flooded the area after the first attack, a second bomber blew up his explosives in the crowd, causing more casualties, Razaq said.
The attacks occurred near the Kandahar airfield where NATO troops in the region are based.
Kandahar is the birthplace of the Taliban and has been the site of fierce fighting between international forces and insurgents.
In another incident overnight, a NATO airstrike killed 18 people in Logar province, said Sahib Khan, a provincial official.
Some of the victims were women and children, but it was unclear whether all the dead were civilians, Khan said.
Lt. Cmdr. Brian Badura, an International Security Assistance Force spokesman, said the ISAF was aware of the claims of civilian casualties and was looking into what took place.
"As of this morning, we did not record any fatalities in Logar, just two injuries," he said.
NATO forces said the strike occurred when soldiers returned fire during a mission targeting a Taliban leader.
"While conducting a follow-on assessment, the security force discovered two women who had sustained nonlife-threatening injuries. The security force provided medical assistance and transported both women to an ISAF medical facility for treatment," a military statement said.
"Multiple insurgents were killed and the Afghan and coalition security force seized several weapons and a quantity of explosives."
The Afghanistan Independent Human Rights Commission, a prominent Afghan human rights body, condemned the killing of civilians in both the suicide attacks and the airstrike.
In a statement, it expressed "deep concerns over the increase of civilian casualties and human rights violations committed by armed groups opposed to the government and in operations conducted by NATO troops."
It also urged "all warring parties to avoid all civilian casualties, and make all possible efforts to avoid harming the lives and property of civilians."
The group put the number killed in the airstrike at 17 and said all of them were women and children.
Meanwhile, the U.S. says it believes that one of its armed helicopters was shot down over neighboring Ghazni province Wednesday, killing both crew members on board, a U.S. military official said.
"It is likely that the helo today was brought down due to enemy small arms and RPG fire," the official said.
The aircraft was a U.S. Army OH-58 Kiowa Warrior reconnaissance helicopter.
In a statement, the Taliban claimed responsibility for the downing of the helicopter, saying a rocket was used.
"After the rocket hit it, the helicopter came down and took fire," said an e-mail sent by Taliban spokesman Zabiullah Mujahid.
The ISAF later said in a statement that two members of its force had been killed in the helicopter crash.
Investigations into the incident are continuing and it is too early to speculate on the cause of the crash, the statement said.
CNN's Mohammed Jamjoom, Ingrid Formanek and Barbara Starr contributed to this report.