The incident occurred around midnight last night and all the four, in the age group of 20-22, were nabbed by local residents and handed over to police, they said.
The accused also attacked one person who attempted to rescue the woman on hearing her alarm.
According to police, the woman had gone to meet her lover at Eesanur tank where three of his friends had assembled for a farewell party by one of them, who had gotten a overseas job.
As she raised an alarm unable to bear the sexual assault, Tirumalai, a local resident, went to her rescue but was hacked with a sickle by the four. He suffered a cut injury.
Police arrested all the four persons today and registered a case of rape and attempt to murder.