MANILA (AFP) - Philippine President Rodrigo Duterte has asked lawmakers to approve the recruiting of 20,000 more soldiers to tackle increased security threats following a bloody urban siege in the south, his spokesman said on Sunday (Aug 6).

Almost 700 people have been killed, according to the official count, in over two months of fighting in the southern city of Marawi against Islamist militants who have pledged allegiance to the Islamic State in Iraq and Syria (ISIS) terrorist group.

The militants, waving the black ISIS flag, have occupied parts of Marawi since May 23, prompting Duterte to declare martial law in the entire southern region of Mindanao.

"The request of the president for additional 20,000 troops is part of our intensified security posture to guard areas in the country where there are continuing security threats," spokesman Ernesto Abella said in a statement.

"The deployment of troops to Marawi and other points in Mindanao needs to be rebalanced to ensure maximum effectiveness," he added.

The Philippine military numbers about 125,000 and faces numerous threats including the ISIS-inspired militants in Mindanao, communist guerrillas scattered all over the archipelago and territorial disputes with China in the South China Sea.

The military is among the region's most poorly-equipped, with only a dozen jet fighters and a fleet composed mainly of second-hand ships.

So many troops have been deployed to Marawi that other parts of the country have expressed concern that they are unprotected.

In a trip to Marawi last week, Duterte asked Congress for the funding for 20,000 additional troops but did not specify how much he needed.

Military spokesman Colonel Edgard Arevalo said on Sunday the defeat of the fighters in Marawi was coming soon but he would not give specifics.

"We are closer there now than before. We can say that we are really at the culminating part of our operations in Marawi," he said.