Former French President Valery Giscard d'Estaing, a key architect of European integration in the early 1970s, has died aged 94 following complications linked to COVID-19. 

Giscard, who had been in hospital several times in the past months for heart problems, died surrounded by his family on Wednesday at their estate in the Loire region, his family said in a statement. 

He ruled France for a single seven-year term from 1974-1981, during which the country made big strides in nuclear power, high-speed train travel and it legalized abortion.

He ensured Paris was at the heart of Europe in a post-war partnership with Germany and also played a key role in what would become the G7 group of major world powers.

Different from his predecessors Georges Pompidou and Charles de Gaulle, he was an accessible and media-savvy modern politician who was comfortable meeting voters, 

His political ambitions though were derailed in 1981 when he lost a tightly contested election to his socialist rival Francois Mitterrand, who would rule France for the next one-and-a-half decades.

"His seven-year mandate transformed France," President Emmanuel Macron said in a statement.

"The direction he set for France still guides our way ... his death has plunged the French nation into mourning."

Macron will address the nation to pay tribute to Giscard at 7 p.m. local time, the Elysee said.

Germany's Chancellor Angela Merkel mourned the loss of a "great European."

Giscard launched a radical reform drive, making it easier for couples to divorce and lowering the voting age to 18, as well as legalizing abortion.

In Europe, Giscard helped move towards a monetary union, in close cooperation with then German Chancellor Helmut Schmidt, launching the system that was a precursor to the euro.

The europhile president was born in the German city of Koblenz, while it was under French occupation in the aftermath of World War I.

It was at his initiative that leaders of the world's richest countries first met in 1975, an event that evolved into the annual summits of the Group of Seven (G7) club.

France's Prime Minister Jean Castex hailed a "man of progress" whose social reforms remained "deeply relevant" for young people and women.

He "succeeded in modernizing political life in France," added former president Nicolas Sarkozy.

Tall and slender, with an elegant, aristocratic manner, he studied at France's elite Ecole Polytechnique and Ecole Nationale d'Administration.

Aged just 18, he joined the French Resistance and took part in the World War II liberation of Paris from its Nazi occupiers in 1944. He then served for eight months in Germany and Austria in the run up to the capitulation of the Third Reich.

He launched his political career in 1959, becoming finance minister in 1969.

With a more relaxed presidential style than his predecessors, "VGE" was sometimes seen in public playing football, or the accordion. 

Giscard involved his family in his political appearances, had the blue and red of France's "tricolor" flag toned down, and the Marseillaise national anthem slowed.

He "dominated almost naturally with his presence, his distinction, his language, his liveliness and intuitions," said fellow centrist Francois Bayrou, a former minister and presidential candidate.

But Macron's predecessor Francois Hollande noted in his tribute that balancing his desire to be a man of the people with his upper-class background and education was not always easy.

"Aware of his great intelligence, which he put at the service of his country, he hoped to appear as a simple president and close to the French. He was not always understood," said Hollande.

After his defeat in 1981 – which he said left him with "frustration at a job unfinished" – Giscard remained active in centrist politics, first regaining a seat in the French parliament and then serving in the European Parliament.

In 2001 he was selected by European leaders to lead work on the bloc's constitutional treaty – which French voters then rejected.

He made one of his last public appearances on September 30 last year for the funeral of another former president, Jacques Chirac, who had been his prime minister.

Giscard's family said that according to his wishes funeral ceremonies would take place in the "strictest intimacy."