An outbreak of Covid-19 has rocked Major League Baseball, forcing the postponement of two games less than a week after the sport launched its season following a four-month coronavirus delay.

Major League Baseball confirmed in a statement that games between the Miami Marlins and Baltimore Orioles in Florida, and the Philadelphia Phillies and New York Yankees in Pennsylvania, had been scrapped.

The decision followed reports that 10 more members of the Marlins - eight players and two coaches - had tested positive for the coronavirus following Sunday's game against the Phillies in Philadelphia.

Four Marlins players - pitcher Jose Urena, first baseman Garrett Cooper, outfielder Harold Ramirez and catcher Jorge Alfaro - had already tested positive for Covid-19.

Major League Baseball said in a statement the games had been postponed in order to allow for additional testing.

"The members of the Marlins' travelling party are self-quarantining in place while awaiting the outcome of those results," the MLB statement said.

The Yankees were due to use the same locker room at Philadelphia's Citizens Bank Park that the Marlins had used over the weekend.

Marlins chief executive Derek Jeter said postponing Monday's game in Florida was the "correct decision." 

"The health of our players and staff has been and will continue to be our primary focus as we navigate through these uncharted waters," Jeter said.

"Postponing tonight's home opener was the correct decision to ensure we take a collective pause and try to properly grasp the totality of this situation."

Jeter said the Marlins had remained in Philadelphia to undergo further testing.

Monday's postponed games came with Major League Baseball less than a week into its abbreviated 2020 season.

The season finally got under way last Thursday four months after it had been due to open in March.  

Games are taking place without fans, while players are subject to a range of strict health and safety protocols designed to prevent outbreaks of Covid-19.

Players are tested for the disease every 48 hours, while masks will be mandatory for all players not on the field of play.

Unlike other sports leagues, such as Major League Soccer and the NBA, which are restarting their seasons with all the teams based at a single location, baseball has opted to leave clubs at their home ballparks, meaning they must travel throughout the United States during the season.

That decision has been criticised as risky by health experts as swathes of the US are battling skyrocketing coronavirus cases.