Pope Francis on Monday called for political leaders imprisoned during Myanmar's coup to be "promptly released", in a speech to ambassadors to the Holy See.

It was his second intervention on Myanmar in two days, after he used the opportunity of his Sunday recital of the Angelus prayer to express his "solidarity with the people" of the country he visited in 2017.

"In these days, my thoughts turn particularly to the people of Myanmar, to whom I express my affection and closeness," the pope said on Monday, according to the official translation of his comments.

"The path to democracy undertaken in recent years was brusquely interrupted by last week's coup d'etat.

"This has led to the imprisonment of different political leaders, who I hope will be promptly released as a sign of encouragement for a sincere dialogue aimed at the good of the country," he said.

Myanmar's generals issued a stern warning against further protests on Monday as a mass uprising against their coup gathered pace, with hundreds of thousands on the streets demanding the release of ousted leader Aung San Suu Kyi. 

The military last week detained Suu Kyi and dozens of other members of her National League for Democracy party, ending a decade of civilian rule and triggering widespread international condemnation.