Game of Thrones to get fifth and sixth seasons after record-breaking return

HBO's hit fantasy TV series will be back for at least another two runs

In demand: Emilia Clarke as Daenerys Targaryen in Game of Thrones (HBO)

Fantasy TV series Game of Thrones has been renewed for a fifth and sixth season, HBO has announced.

Based on George RR Martin's popular A Song of Ice and Fire novels, the small screen adaptation has become "a phenomenon like no other", according to Michael Lombardo, HBO programming president.

Announcing the return of the show, Lombardo said: "David Benioff and DB Weiss, along with their talented collaborators, continue to surpass themselves, and we look forward to more of their dazzling storytelling."

HBO's hit show began its fourth season on Sunday night, attracting record ratings of 6.6 million, the highest figure since The Sopranos finale in 2007.

Creators David Benioff and DB Weiss told Vanity Fair in March that they would consider bringing Game of Thrones to an end after seven or eight runs.

"We know there's an end somewhere in the seven or eight season zone," said Weiss. "It's not something that goes 10, 11 - it doesn't just keep on going because it can. I think the desire to milk more out of it is what would eventually kill it, if we gave in to that."

Benioff has described season four as "the pivot point", meaning fans should expect plenty of drama and excitement.

The pair have reportedly met with Martin to "talk through where things are going", in order to understand where they stand and whether they will be able to "catch up".

"I'm hopeful that I can not let them catch up with me," said Martin.

The US author has previously suggested that feature films may be required to conclude the HBO series.

"Something with a feature budget, like $100 million for two hours," he told The Hollywood Reporter at the new season's New York premiere. "Those dragons get real big, you know."