Eight-time champions Dhofar crashed out on penalties 3-4 against two-time winner Saham at the Sohar Sports Complex on Sunday after both the teams were locked in a 1-1 stalemate at the end of regulation time.
Earlier on Friday, Al Arouba, also met a similar fate as it also made a shock exit against first division side, Nizwa, at its home ground in Sur. A four-time champion, Al Arouba, was held to a 1-1 draw by unfancied Nizwa in front of its own fan and then lost 3-4 on penalties.
Another Omantel League side, Al Nahda, also bowed out at its home ground in Buraimi as it went down to four-time champions Al Nasr 1-3 on penalties after the two top-flight teams were involved in a 1-1 draw.
Other Omantel League sides to make exits included Al Salam, which lost to Sur 0-1 at Sohar Sports Complex on Friday, and Muscat, which lost 0-3 to Al Bashayer at the ROP Stadium on Saturday.
The teams that advanced to round of 16 on Friday were Al Rustaq, Samail, Al Shabab, Sohar and five-time winners Ahli-Sidab.
Also progressing into the next stage on Saturday were three-time champions Seeb, Bidiyah and Oman, which got the better of Mirbat on penalties 6-5 after the teams were locked in a 1-1 draw in Salalah.
Defending champion and current Omantel League leader Al Suwaiq faces Quriyat, a first division side, in a late game on Sunday.
Also, record nine-time champions Fanja face Omantel League debutant Mudhaibi in a tricky clash in a late game along with Jalan, which meets Al Wusta.
Other round of 32 results: Friday: Al Rustaq 2 Al Ittefaq 1, Samail 1 Mussanah 0, Al Shabab 2 Majees 0, Bausher 1 Ahli-Sidab 2, Sohar 3 Bahla 0.
Saturday: Seeb 2 Salalah 0, Bidiyah 3 Al Ittihad 1.