Outgoing Greek prime minister's party suffers further defections ahead of September elections

Outgoing Greek Prime Minister Alexis Tsipras listens to the Archbishop of Albania during their meeting in Athens, Tuesday, Aug. 25, 2015. Tsipras resigned on Thursday, Aug. 20, following a rebellion in his party over Greece's new bailout, which saw dozens of Syriza lawmakers dissent when the deal came to a vote in Parliament. (AP Photo/Petros Giannakouris) (The Associated Press)

Outgoing Greek Prime Minister Alexis Tsipras stands outside his office during the arrival of the Archbishop of Albania in Athens, Tuesday, Aug. 25, 2015. Tsipras resigned on Thursday, Aug. 20, following a rebellion in his party over Greece's new bailout, which saw dozens of Syriza lawmakers dissent when the deal came to a vote in Parliament. (AP Photo/Petros Giannakouris) (The Associated Press)

ATHENS, Greece – A large block of hardline leftwing officials has left Greece's dominant Syriza party, highlighting the challenges Prime Minister Alexis Tsipras faces ahead of national elections next month.

A total of 53 members of the 201-strong central committee — the main party organ — announced their resignations Wednesday. They all back the Popular Unity party formed by disaffected Syriza officials. The party, led by former Energy Minister Panagiotis Lafazanis, is currently the third-largest in parliament with 25 former Syriza lawmakers.

Tsipras resigned last week after seven months in power, seeking a stronger mandate in elections expected Sept. 20.

His move followed a party rebellion triggered by his acceptance last month — against Syriza's key policy commitments — of new austerity measures to secure Greece a vital third international bailout.