Although Niki Lauda once said he has no real friends, plenty of them are paying emotional tribute to the inimitable F1 legend this week.

"Niki always had his own opinion," an emotional Bernie Ecclestone told Blick newspaper. "And that is very rare in Formula 1."

The former F1 supremo said he visited Lauda, who was 70 when he died on Monday, in late April.

"I visited him in Switzerland and he was already very weak," Ecclestone said. "I was really worried.

"Now he is not suffering anymore. He was allowed to leave this world with pride, which is certainly better for him."

Austria's Kurier newspaper said one of Lauda's closest lifetime friends was Bertl Wimmer, who saw the Mercedes team chairman two weeks ago.

"He was feeling sick," he said. "They took him to Switzerland and from there I could not reach him anymore.

"He was very emaciated when I saw him the last time. He had realised that he would not easily recover.

"But he was a fighter and he didn't want to believe it. But at some point he realised that he had no more chance," Wimmer added.

Dr Helmut Marko, the Red Bull boss, told ORF television that he spoke on the phone with Lauda very recently.

"He spoke in a very weak voice," said the Austrian.

"There had already been some critical situations. It was not about whether he would return to Formula 1, but whether he survived."

Marko said Lauda leaves an "irreplaceable gap" in Formula 1 and beyond.

Another of Lauda's closest friends was Arturo Merzario, who was among those who saved the then Ferrari driver from the flames at the Nurburgring in 1976.

"I last telephoned him about a month ago. He was really exhausted," he said.

Merzario is among those who believe that, along with Toto Wolff, Lauda was a guiding light of Mercedes' F1 dominance.

"I am worried that without Niki, decisive decisions will be taken. I hope I'm wrong," he said.

Lauda was born in and loved Vienna, and the city has announced that a grave of honour - one of just 1000 - will be offered to the triple world champion.

"Ultimately it is a decision of the family whether they accept it," said a city spokesman.

But friend Wolfgang Fellner said Lauda actually died in Zurich.

"He moved to Lucerne two months ago," he said. "Then came the relapse. Ten days ago he was transferred to the hospital in Zurich.

"He went on dialysis and I think also the respirator. He had to fight for survival."

Alain Prost, once Lauda's teammate at McLaren and a friend, told L'Equipe in France that he is "in shock".

"I didn't think it would affect me this much," he admitted.

"There are champions, but we have lost a gentleman who never complained about his condition. He was someone who always looked ahead," said Prost.