Bangkok: Philippine troops are planning a final assault to end the almost 100-day battle of Marawi, as Islamic State-allied fighters try to sneak into the besieged southern Philippine city.

More than a dozen armed militants have been killed in firefights with soldiers in recent days as they attempted to cross the city's Lake Lanao under the cover of darkness.

It is not known how many have managed to reach the 40 or so heavily-armed militants still holed up in the city centre with hostages.

Militants have also attacked residents in the nearby town of Marantao in what analysts say appears to be a ploy to divert military attention from Marawi.