The death toll from two days of militant bombings neared 140 — the deadliest spate in post-Taliban Afghanistan — after a homicide car bomb exploded in a crowded southern market Monday, killing 38 Afghans, officials said.

The marketplace bombing, which targeted a Canadian military convoy, came one day after Afghanistan's deadliest insurgent attack since the Taliban's ouster in 2001. The toll from that blast — set off in a crowd watching a dog fight — rose to more than 100 Monday.

The back-to-back bombings in Kandahar province could serve as a warning that insurgents have turned to collateral civilian deaths to further weaken the Kabul government. Though attacks occasionally have killed dozens, insurgents in Afghanistan have generally sought to avoid targeting civilians, unlike attacks that have scarred Baghdad in recent years.

The attacks come amid warnings that Afghanistan this year could fall victim to even more violence than in 2007, when a record 6,500 people — mostly militants — were killed. The U.S., with a record high 28,000 troops in the country, is sending 3,200 more Marines in April.

The Taliban, which has denied it carried out Sunday's attack, immediately claimed responsibility for the marketplace bombing, which took place in the town of Spin Boldak about 90 meters (100 yards) from the border with Pakistan.

"The attacks show that the enemies of Afghanistan are changing their tactics. Now they are not thinking about civilians at all," said Nasrullah Stanikzai, a professor of political science at Kabul University.

"They wanted to cause such big casualties in these attacks to weaken the morale of the government and the international community, to show the world the Afghan government is too weak to prevent them," he said.

Hours before the marketplace bombing, Kandahar Gov. Asadullah Khalid raised the toll from Sunday's bombing from about 80 to more than 100, saying some of the scores of critically wounded had died. Khalid said 38 were killed and 28 wounded in Monday's attack. Three Canadian soldiers were also wounded, NATO's International Security Assistance Force said.

The governor also complained that the Canadian forces had failed to heed government warnings to stay away from the border with Pakistan.

"We informed the Canadian forces to avoid patrolling the border areas because our intelligence units had information that suicide attackers were in the areas and wanted to target Canadian or government forces," he said. "Despite informing the Canadians, they went to those areas anyway."

A spokesman for the Canadian military couldn't be reached, and a spokesman for NATO's International Security Assistance Force said he had no details on the matter.

Though the Afghan-Pakistan border had been closed Monday because of elections in Pakistan, some of the wounded were taken to a hospital in Chaman, Pakistan just across the border for treatment. One of them, Abdul Hakim lay in a hospital bed, his clothes caked with dust and splattered with blood.

"A white Toyota Corolla car rammed the second vehicle in the convoy as it passed through the bazaar," said Hakim, who witnessed the attack from his grocery store. "Then there was a huge explosion. It was dust. I do not know what happened to me."

One of the Canadian military vehicles was heavily damaged in the attack, as were several shops and civilian vehicles, said Abdul Razeq, the Spin Boldak border police chief.

When asked about the large number of civilians killed, Taliban spokesman Qari Yousef Ahmadi claimed that 10 foreign soldiers and "a large number of police" were killed. The Taliban often make false or exaggerated claims that their attacks killed NATO or U.S. troops.

Meanwhile, Afghans buried relatives and friends who died in Sunday's attack. Officials said the attacker targeted an anti-Taliban militia leader, Abdul Hakim Jan, who died along with 35 of his men, who served on a government auxiliary police force.

Khalid, the Kandahar governor, told mourners at a mosque he had warned Jan about three weeks ago that militant homicide bombers were trying to kill him. Government officials haven't identified any suspects in the attack.

Antonio Giustozzi, a London School of Economics researcher and Afghanistan expert, said it couldn't be ruled out the attack was carried out by one of Jan's tribal rivals.

Kandahar — the Taliban's former stronghold and Afghanistan's second-largest city — has been the scene of fierce battles between NATO forces and Taliban fighters the last two years.

The province, one of the country's largest opium producing regions, could again be a flash point in the increasingly violent Afghan conflict this year.

The previous deadliest bombing in Afghanistan killed about 70 people — mostly students — in November, part of a record year of violence in 2007 that included more than 140 homicide attacks.

Separately, a British soldier was killed and another wounded when their patrol was struck by an explosion Sunday in southern Afghanistan, Britain's Ministry of Defense said Monday.