La Liga sides Athletic Bilbao and Real Betis booked their places in the Spanish Cup last 16 with comfortable wins over lower-tier opponents on Thursday.

Athletic, who have won the trophy 23 times -- more than any side other than Barcelona -- thrashed third division Eldense 6-1 in the round of 32.

Spain international Nico Williams broke the deadlock with Alejandro Berenguer netting a brace and Oier Zarraga helping to ramp up the score.

Mario Soberon pulled one back for Eldense but a Ruben Machado own goal saw Athletic net their fifth, before Iker Muniain rounded off the rout.

Real Betis cruised to a 4-1 win over fourth tier CD Ibiza, although they had to come from behind to triumph.

Jose Miguel Bernal sent the minnows ahead in the 26th minute after a defensive slip-up, but a Betis onslaught after the break helped them progress to the last 16.

Willian Jose levelled from close range in the 54th minute and four minutes later Edgar Gonzalez turned the game on its head with a flicked finish.

Iker Murua put through his own net to extend Betis's lead and playmaker Nabil Fekir added a late fourth.

La Liga side Osasuna needed extra-time to beat third division Gimnastic 2-1, with Eric Montes's own goal deciding the game.

Kike Garcia sent Osasuna ahead a few minutes after Chimy Avila hit the post with a sensational volley, but Pablo Fernandez levelled with a towering header in the 78th minute, six minutes before being sent off.

On loan Barcelona winger Ez Abde forced the Montes own goal with a cross from the left across the six-yard box.

Osasuna's Pablo Ibanez was also dismissed in the final stages of the additional period, with both sides finishing on 10 men.

Record 31-time winners Barca, Real Madrid and Atletico Madrid secured their spots in Saturday's last 16 draw earlier in the week.