Malaysia's defence minister on Thursday rejected a ceasefire offer by a self-styled Philippine sultan unless his fighters who launched a deadly incursion "surrender unconditionally".
"A unilateral ceasefire is not accepted by Malaysia unless the militants surrender unconditionally," Defence Minister Ahmad Zahid Hamidi said on his Twitter feed.
The "sultan", Jamalul Kiram III, had declared a unilateral ceasefire for 12:30 pm (0430 GMT), calling for reciprocation from Malaysia, whose armed forces are currently on the hunt for the invaders in a remote corner of Borneo island.
Kiram sent his followers from their southern Philippine island homes across the Sulu Sea to assert an ancestral claim to the Malaysian state of Sabah, located on Borneo's northern tip.
At least 28 people -- 20 militants and eight police officers -- have been reported killed since an initial stand-off began more than three weeks ago in the sleepy farming village of Tanduo.
Zahid added: "Don't believe the ceasefire offer by Jamalul Kiram. In the interest of Sabahans and all Malaysians, wipe out all the militants first."
Jamalul's ceasefire call came after UN Secretary General Ban Ki-moon urged a peaceful resolution to the bizarre incursion, Malaysia's biggest security crisis in years.
It also coincided with a sudden visit to the area by Malaysian premier Najib Razak to inspect security operations.
Najib's government tried for three weeks to persuade the invaders to leave but launched a military assault Tuesday after they continually refused and engaged security forces in a pair of deadly shootouts.