KABUL, July 29 (Xinhua) -- Afghanistan's capital Kabul witnessed a deadly terrorist attack on Sunday, the first day of the start of presidential election campaign in the country plagued by conflict.

In the deadly attack, launched by a group of militants at 4:40 p.m. local time on Sunday on the office of vice president candidate Amrullah Saleh, according to Interior Ministry spokesman Nasrat Rahimi, 24 people, including four attackers, were killed and 50 others injured.

"The terrorists' attack against the people of Afghanistan here on Sunday claimed the lives of 20 innocent people and injured 50 others," Rahimi told Xinhua on Monday.

Those killed in the attack include four security personnel and 16 civilians, Rahimi said, adding that those injured include 43 civilians and seven security personnel.

All the four attackers had also been killed after hours of clean-up operations, the official said.

The deadly attack claimed by no militant group so far, coincided with the start of Afghan presidential election campaign, when the contesters including the incumbent President Ashraf Ghani vowed to bring peace to the conflict-torn country at rallies of their supporters.

In his address at a rally on Sunday, Ghani promised to strengthen the government to stabilize economy and bring about peace and prosperity if re-elected.

The 60-day Afghan presidential election campaign, which started on July 28 with 18 candidates including Ghani amid increasing security risks and fear of fraud in the polls, will end on Sept. 28.

Meanwhile, rival candidates including Chief Executive Abdullah Abdullah and former intelligence chief Rahmatullah Nabil have accused Ghani of using government facilities for the campaigns.

Locals slam the government over what they described as "security lapse," calling upon the security apparatus to protect the lives and properties of people during elections.

"Some of the victims even don't have money to rebuild their houses damaged by the blast on Sunday," Kabul resident Samiul Haq told Xinhua.

Another man Dawlat Khan, 26, told Xinhua on Monday that he had got mental problems since the blast and gunshot took place on Sunday, saying, "security is more important than everything and the government first has to stabilize security and then hold elections."