Vietnam's Communist Party delegates are meeting in Hanoi to begin the process of choosing a new set of leaders.

The congress, which happens once every five years in the one-party state, will run for eight days.

Behind closed doors, the 1,500 members will nominate the next president, the prime minister, and most importantly, the party's general secretary.

Who wins could determine Vietnam's relations with key partners including the US and China.

Media, which is closely controlled in Vietnam, are not allowed to cover the congress except for the opening ceremony.

On Thursday, top leaders gave brief speeches emphasising the need to build Vietnam's economic prosperity, and also reviewed the leadership of the central committee, reported newspaper Viet Nam News.

'Ominous' turtle death on the eve of congress - Nga Pham, BBC News

Cu Rua was not only beloved by Hanoi residents but by Vietnamese all over the country

Vietnam is mourning an ancient turtle whose death has shocked the country.

Thought to be one of only four living Yangtze giant softshell turtles, Cu Rua was found floating in the Hanoi lake where it lived. Cause of death is unclear.

To many of Hanoi's residents, Cu Rua was more than a charming local character - its appearances at the same time as some of the country's biggest events, such as Hanoi's 1,000-year anniversary, were seen as auspicious - while ailments were seen as ominous signs.

The issue of Cu Rua's death was so delicate that state censors briefly tried to prevent the news from being reported.

"To cheerfully welcome the party congress, newspapers and media please do not report on the turtle's death for now," the party's propaganda department instructed.

The competition for the general secretary job pits current Prime Minister Nguyen Tan Dung, seen as modern and friendly towards the US, against party stalwart and incumbent, Nguyen Phu Trong.

Mr Dung has gained popularity domestically with strong anti-China rhetoric when it comes to disputed territory in the South China Sea.

Mr Trong is seen to be more friendly towards China - Vietnam's largest trading partner.

The congress takes place amid resurgent tension with China. On Tuesday, Vietnam said it had demanded China remove a controversial oil rig parked in waters claimed by both countries.

In 2014, Beijing moved the same rig into contested waters, sparking violent anti-Chinese protests in Vietnam.

Delegates at the Congress will set key policies for the next five years, including on Vietnam's economic strategy.

They will also elect a new central committee. Near the end of the event, that new committee will elect a politburo from within its ranks and select one person as party general secretary.

The prime minister, president and national assembly chairman - the three other top positions - will be nominated, but their formal selection is made by the national assembly, which is not elected for another six months.