MANILA -- (UPDATED) Chief Justice Teresita Leonardo-De Castro assumed the top post in the Supreme Court on Tuesday, ahead of oral arguments on a petition contesting the Philippines' withdrawal from the International Criminal Court.

Court employees congratulated De Castro with flowers, balloons and tarpaulins. Her appointment by President Rodrigo Duterte was announced over the weekend.

The new Chief Justice took her oath during an en banc session after the high court received her appointment paper from Malacañang, said court administrator Midas Marquez.

Read: Appointment of Teresita De Castro as Supreme Court Chief Justice pic.twitter.com/aVqRHX24XK

— Pia Gutierrez (@pia_gutierrez) August 28, 2018

De Castro, 69, replaced Maria Lourdes Sereno, whom she helped oust last May over allegations she failed to fully disclose her wealth.

• De Castro appointment solidifies Sereno ouster: IBP

• THROWBACK: Sereno, De Castro in fiery exchange at oral arguments on ouster petition

Sereno, who had been at odds with Duterte, also faced a separate impeachment complaint but she was ousted through an unprecedented "quo warranto" proceedings initiated by Solicitor General Jose Calida.

Mga empleyado ng Korte Suprema, may pa-welcome kay bagong Chief Justice Teresita Leonardo-De Castro ngayong Martes ng umaga; ilalabas ang kanyang appointment ngayong araw at nakatakda siyang manumpa bilang ika-24 punong mahistrado sa Agosto 31. (📸: SC PIO) | @dzmmRP45 pic.twitter.com/8RFUV9fM5B

— DZMM TeleRadyo (@DZMMTeleRadyo) August 28, 2018

Tarp and balloons greet Chief Justice De Castro at the Supreme Court: pic.twitter.com/qmg86Y9P9I

— Ina Reformina (@InaReformina) August 28, 2018

Duterte in March pulled out Manila from the Rome Statute that created the ICC after the court announced that it would investigate alleged mass murders under his anti-narcotics drive.

• Can Duterte pull out PH from ICC?

• 'No reason' for Supreme Court to reject ICC advocates plea: Rosales

Next week, De Castro is expected to face impeachment hearings together with 6 other Supreme Court justices for booting out Sereno and allegedly usurping the power of Congress to remove impeachable officers.

• Impeach hearings vs newly appointed Chief Justice may start next week - solon

Outside the Supreme Court, a small group of protesters hold up plackards vs CJ De Castro appointment pic.twitter.com/nrWpPuIZUF

— Ina Reformina (@InaReformina) August 28, 2018

De Castro is expected to serve only until October 8 when she reaches the mandatory age of retirement of 70.

• PROFILE: Teresita De Castro

With reports from Dexter Ganibe and Ina Reformina, ABS-CBN News