A thin-looking Kim Jong Il made a rare public appearance Wednesday as North Korea paid solemn respects to his father, the country's late founder, on the 15th anniversary of his death.

The memorial was the second major state event that the 67-year-old Kim has attended in person since reportedly suffering a stroke last summer. In early April, he presided over a parliamentary meeting where he was re-elected as leader.

Footage from broadcaster APTN showed Kim dressed in a khaki suit, looking more gaunt and with less hair than in April. As in April, he limped slightly while walking into the packed Pyongyang auditorium in what is believed to be an effect from the stroke.

Kim bowed his head during a moment of silence. A portrait of a giant red flag with an image of his father, a smiling Kim Il Sung, dominated the backdrop.

Kim's health has sparked concerns about instability and a power struggle if he were to die without naming a successor. His third and youngest son, Kim Jong Un, has widely been reported as being groomed as heir, but the regime has made no announcement to the outside world.

Wednesday's memorial came after the North conducted a number of banned ballistic missile tests last weekend, fueling tensions already running high after Pyongyang's second nuclear test on May 25 led to punishing U.N. sanctions.

The regime used the memorial to criticize the United States and South Korea.

"We will sternly smash the U.S. imperialist forces and South Korea's puppet regime anti-unification plot," Kim Yong Nam, the North's No. 2 leader, told the ceremony, according to footage broadcast on state television.

"We will achieve the historical mission of national unification by realizing" Kim Il Sung and Kim Jong Il's policies for that, he added.

Kim Il Sung died of heart failure on July 8, 1994 at the age of 82. He ran the communist country with an iron grip and was the object of an intense personality cult.

Streams of North Koreans visited a huge bronze statue of their late founder standing on a hill overlooking the capital. They laid flowers and bowed repeatedly.

"The great leader, President Kim Il Sung, is always alive _ not only in the hearts of our people, but also in the minds of people all over the world," said Hwang In San, a Pyongyang resident.

The North's Korean Central News Agency reported that the younger Kim visited the Kumsusan Memorial Palace in Pyongyang, where Kim Il Sung's embalmed body lies, accompanied by top military generals.

Kim Jong Il assumed power after his father's death, though he did not take on his father's title of president. He runs North Korea from his post as chairman of the National Defense Commission.

In Seoul, dozens of conservative South Korean activists staged an anti-North Korea rally, torching a North Korean flag covered with crossed-out photos of Kim Il Sung, Kim Jong Il and Kim Jong Un.

The rally took place in front of the home of former South Korean President Kim Dae-jung, who held the first-ever inter-Korean summit with Kim Jong Il in 2000. Protesters accused the former president of providing the North with massive aid and helping fund Pyongyang's nuclear and missile programs.

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Associated Press writers Jae-soon Chang, Hyung-jin Kim, Kelly Olsen and AP Television News cameraman Yong-ho Kim in Seoul, South Korea, contributed to this report.