The death toll from a suicide bombing attack in Kabul on Saturday (local time) currently is at least 29 people killed and 142 wounded.
Graphic television footage from the site of the blasts showed many dead bodies lying on the bloodied road, close to where thousands of Hazara had been demonstrating on Saturday over the route of a planned multi-million dollar power line.
Mohammad Ismail Kawousi, a spokesman for the ministry of public health, said at least 29 dead and 142 wounded had been taken to nearby hospitals but the numbers may change.
It was not immediately clear how many bombs were involved in the attack.
Emergency vehicles were at the site and wounded were being carried away.
Much of the city centre had been sealed off with stacks of shipping containers and other obstacles as the march began earlier on Saturday, and security was tight with helicopters patrolling overhead.
There was no immediate claim of responsibility for the blasts, which came some three weeks after a suicide bomber killed dozens of people in an attack on newly graduated police cadets that was claimed by the Taliban.
"Opportunist terrorists went among the protesters and set off explosions that killed and wounded a number of our countrymen including security and defence personnel," President Ashraf Ghani said in a statement.
Saturday's demonstrators had been demanding the 500kV transmission line from Turkmenistan to Kabul be rerouted through two provinces with large Hazara populations, an option the government says would cost millions and delay the badly needed project by years.
The Persian-speaking Hazara, a mainly Shia group estimated to make up about nine per cent of the population, are Afghanistan's third-largest minority but they have long suffered discrimination.
Thousands were killed under Taliban rule.
The protest by a group whose leaders include members of the national unity government had put pressure on President Ashraf Ghani, who has faced growing opposition from both inside and outside the government.
It also risked exacerbating ethnic tensions with other groups and provinces the government says would have to wait up to three years for power if the route were changed.
The transmission line, intended to provide secure electricity to 10 provinces, is part of the so-called TUTAP project backed by the Asia Development Bank, linking energy-rich states of Central Asia with Afghanistan and Pakistan.
Hazaras say they want the line to come through Bamyan and Wardak provinces, west of Kabul, where many Hazaras live, to ensure their power supply.