KUALA LUMPUR, Malaysia (AP) — Malaysian police have detained 12 activists ahead of a rally by electoral reform group Bersih seeking Prime Minister Najib Razak's resignation over a financial scandal.

Security has been tightened Saturday with key roads barricaded in downtown Kuala Lumpur where Bersih and a pro-government group plan to rally despite a police ban.

Bersih said on Twitter that police raided its office on Friday and detained its chairwoman Maria Chin and another official. It says at least seven others including politicians have also been held.

Ruling party politician Jamal Mohamad Yunos, who plans to lead a counter rally, also has been detained with two other anti-Bersih activists, Jamal's group said in a statement.

Najib has kept an iron grip amid graft allegations involving the indebted 1MDB state fund that he founded.