South Korea's main opposition party has selected its candidate for the December presidential election.

The Democratic United Party picked former human rights lawyer and former presidential aide Moon Jae-in on Sunday.

In his acceptance speech, Moon vowed to push for summit talks and greater economic cooperation with North Korea.

The liberal party candidate served as chief of staff for the late President Roh Moo-hyun, who held summit talks with the north in 2007.

Moon faces the ruling party's presidential candidate Park Geun-hye, the daughter of slain former dictator Park Chung-hee.

Opinion polls show Park leading in the race. If elected, she would become South Korea's first woman president.