North Korea marked the 70th anniversary of its ruling Workers' Party on 10 October with a massive military parade overseen by leader Kim Jong-un and a senior Chinese official who had delivered President Xi Jinping's call for stronger ties between the states.

Thousands of troops stood at attention in perfect formation under a blue autumn sky in Pyongyang's main Kim Il-sung Square, named after Kim Jong-un's grandfather and the founder of the nation, as its leader Kim Jong-un made his way to the podium.

Kim was accompanied by senior Chinese Communist Party official Liu Yunshan and flanked by senior North Korean party and military officials.

Troop carriers could be seen mobilizing soldiers for the parade, expected to be one of the largest held by North Korea, which has been slapped with UN and US sanctions for its nuclear weapons and rocket programmes.

Impoverished North Korea and rich, democratic South Korea, backed by the US, remain technically at war after their 1950-53 conflict ended in a truce, rather than a peace treaty.

In a letter delivered by Liu, the most senior Chinese official to visit Pyongyang since leader Kim came to power following his father's death in 2011, President Xi said China attached vital importance to its relationship with North Korea, China's official Xinhua news agency said.

Kim Jong-un North Korea
Kim Jon-un has been ruler of the North Korea's Workers' Party since April 2012 Reuters

China is North Korea's chief ally and its main trading partner, although ties have been strained over the country's nuclear programme.

Xi said in the letter that China had "been striving to treat the bilateral relations from a strategic and long-term perspective". Liu reiterated China's position that it wanted an early resumption of the so-called six-party talks aimed at reining in North Korea's nuclear ambitions.

"The Chinese side is willing to seek closer communication and deepen cooperation, pushing for a long-term, healthy and stable development of the Sino-DPRK ties," Xi said in the letter cited by Xinhua, referring to North Korea by its official name, the Democratic People's Republic of Korea.

Kim, who is in his early 30s, told the visiting Chinese delegation on 9 October that North Korea was also keen to bolster ties, the North's official KCNA news agency said on Saturday.

Liu is the fifth-ranked member on China's ruling Communist Party's elite Politburo Standing Committee.