Citizens grieve as they file past a portrait of late North Korean leader Kim Jong-il on display in the plaza of the Pyongyang Indoor Stadium on Wednesday. Image Credit: AP

Pyongyang, North Korea: Tens of thousands of mourners packed Pyongyang's snowy main square yesterday to pay respects to late leader Kim Jong-il as North Korea tightened security in cities and won loyalty pledges from top generals for Kim's son and anointed heir.

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 Kim's father, North Korean founder Kim Sung-il, usually hangs.

Kim died of a heart attack Saturday, according to state media, which reported his death on Monday.

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 Kim's honour, just below the spot where he stood last year waving to crowds at the massive military parade where he introduced his successor, Kim Jong-un.

High alert

Two medical workers rushed to carry away a woman who had fainted.

"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 yesterday that North Korea was consolidating power behind Kim's untested, 20-something son.

Worries around Northeast Asia have risen sharply as Kim rises to power in a country with a 1.2-million troop military, ballistic missiles and an advanced nuclear weapons development programme.

South Korea has put its military on high alert. In another sign of border tension, Chinese boatmen along a river separating North Korea and China said that North Korean police have ordered them to stop giving rides to tourists, saying they will fire on the boats if they see anyone with cameras.

Along the Koreas' border, the world's most heavily armed, South Korean activists and defectors launched giant balloons containing tens of thousands of propaganda leaflets, a move likely to infuriate the North. Some of the leaflets opposed a hereditary transfer of power in North Korea. Some showed graphic pictures of former Libyan leader Muammar Gaddafi's battered corpse and described his gruesome death. Seoul's National Intelligence Service believes the North is now focused on consolidating the younger Kim's power and has placed its troops on alert.