KABUL (Reuters) - Some 80 people died in Tuesday's bomb attacks on Shi'ite Muslim ceremonies in Afghanistan, far higher than the previously reported number, Afghan President Hamid Karzai said Sunday.

"The numbers I got this morning, it is 80 people who died," he said, speaking at a government event in the capital.

It was not clear whether he was referring only to the bombing at a shrine in Kabul, which police said Tuesday had killed 55, or including two other incidents in different cities.

The original toll given for all three incidents -- in Kabul, northern Mazar-i-Sharif, and southern Kandahar -- was 59 people.

Tuesday was one of the deadliest days for civilians since the U.S.-led overthrow of the Taliban government in 2001.

Over 80 people were killed in a suicide attack in southern Kandahar province in early 2008, the same year that 58 people died in a suicide car bomb attack on the Indian embassy in Kabul.

But the attacks last week are the first tainted with sectarianism, and have raised fears among some that more violence between Sunni and Shi'ite Muslims is to come.

Such attacks are common in Pakistan and Iraq, but despite Afghanistan's decades of war and ethnic tensions, the country has not suffered large-scale attacks on the minority Shi'ites since the fall of the Taliban.

Saturday, the U.S. ambassador to Afghanistan said he did not think a sectarian conflict was likely to break out.

Karzai said after the attacks that Pakistan-based group Lashkar-e-Jhangvi had claimed responsibility, and that he would raise the matter with the Pakistan government.

(Reporting by Mirwais Harooni; Writing by Daniel Magnowski, editing by Emma Graham-Harrison and Sanjeev Miglani)