Women held handkerchiefs to their faces as they wept and filed past a huge portrait of a smiling Kim Jong-il hanging on the Grand People’s Study House, in the spot where a photograph of his father, Kim Il-sung, usually hangs.
Kim Jong-il died of a massive heart attack on Saturday, according to state media.
A huge crowd of mourners converged on Kim Il-sung Square with traditional white mourning flowers in hand.
The crowd grew throughout the day, even as heavy snow fell, and some mourners took off their jackets to shield mourning wreaths set up in Mr Kim’s honour.
“We chose to come here to care for citizens who might faint because of sorrow and mental strain,” Jon Gyong Song, 29, who works as a doctor in a Pyongyang medical centre, said. “The flow of mourners hasn’t stopped since Tuesday night.”
South Korean intelligence reports, meanwhile, indicated that North Korea was consolidating power behind Mr Kim’s untested son, Kim Jong-un. The region is on alert as power is transferred to the dictator’s son. North Korea has 1.2 million troops, ballistic missiles and an advanced nuclear weapons programme.
South Korea has put its military on high alert. Chinese boatmen along a river separating North Korea and China said North Korean police ordered them to stop giving rides to tourists, saying they would fire on the boats if they saw anyone with cameras.
Kim Jong-il ruled North Korea for 17 years after inheriting power from his father, national founder and eternal North Korean president Kim Il-sung, who died in 1994.
Kim Jong-un only entered the public domain last year and remains a mystery to most of the outside world. South Korea’s National Intelligence Service (NIS) believes the North is now focused on consolidating his power and has placed its troops on alert, Kwon Young-se, a member of the South Korean parliament, said.
South Korean military officials said North Korea has ordered its troops to be vigilant but that it didn’t mean they were being mobilised.
Mr Kwon said the NIS had told the parliamentary intelligence committee that senior military officials have pledged allegiance to Kim Jong-un, and that more security officers have been deployed in major cities across North Korea.
Initial indications coming out of North Korea suggest the power transition to the son has been moving forward, though it remains unclear when Kim Jong-un will formally assume power.
According to official media, more than five million North Koreans have gathered at monuments and memorials in the capital since the death of Kim Jong-il.
Hundreds of thousands visited monuments around the city within hours of the official announcement of his death.
The North has declared an 11-day period of mourning that will culminate in his state funeral and a national memorial service on 28-9 December.