An extra 250 policemen from Ipoh will now join increased patrols at churches and mosques in Penang following this morning's Molotov cocktail attack at the Church of the Assumption in George Town.

Penang Chief Minister Lim Guan Eng said the precautionary mesaures was given to him by the Penang police chief Abdul Rahim Hanafi.

The Catholic church was attacked after a controversial banner with the words "Allah" was found outside it before Sunday Mass.

Only one of the petrol bombs exploded while the other fell on the grass, he said.