Venezuelan President Nicolas Maduro said his government has received an asylum application from US intelligence leaker Edward Snowden and the fugitive must now decide if he wants to fly to Caracas.

"We have received the asylum request letter," Maduro said on Monday from the presidential palace. "He will have to decide when he flies, if he finally wants to fly here."

Over the weekend, Venezuela, Nicaragua and Bolivia all offered political asylum to Snowden, who has spent more than two weeks stranded at Moscow's international airport while waiting for a country to give him sanctuary.

"We told this young man, 'you are being persecuted by the empire, come here,'" Maduro said Monday, referring to the United States.

Bolivia, meanwhile, had earlier demanded France, Spain, Italy and Portugal explain why they refused permission for President Evo Morales to cross their air space last week.

His plane was forced to make an unplanned stop in Vienna after four countries refused to allow it to fly through their airspace, apparently on suspicion that Snowden was aboard his aircraft.

"The Bolivian government has summoned the ambassadors of Spain, France, Italy and Portugal to explain what happened to the presidential plane and President Evo Morales," Communications Minister Amanda Davila said on Monday.

"It's the first case of state terrorism against a president, against a nation, against a people. That's what we're talking about now" she said.

She said the government had decided to "initiate all necessary actions until it has a clear explanation and a direct and unambiguous apology by those countries".

Morales said on Saturday that he would grant asylum to Snowden, if the US whistleblower requests it.

He emphasised that his offer is a protest against the US and European nations whom he accused of temporarily blocking his flight home.

The offers have raised hope the US whisteleblower might be finally able to leave Russia, though it remains unclear how exactly Snowden could reach another country without legal documents. The US revoked his passport after he fled to Moscow from Hong Kong.

Snowden apparently applied to 21 countries for asylum, but most of them have since declined to accept his request.