AFP-- Three times in the past 10 days Taliban and ISIS extremists have penetrated heavily fortified areas in Afghanistan's capital to carry out attacks that have killed and wounded hundreds of people, including foreigners.

The extremists' chilling ability to hit at the heart of the country despite increased police checks has put security and intelligence failures in the spotlight.

After the latest assault Monday, an ISIS-claimed attack on an army battalion that killed at least 11 soldiers, President Ashraf Ghani pledged in a tweet that "reforms in our intelligence services and Ministry of Interior are our top priority now".

But as public anger swells, security officials are on the defensive.

"The terrorists are changing their tactics," Mohammad Masoom Stanekzai, the head of Afghanistan's spy agency, told reporters on Sunday.

"It does not mean a lapse (in security). We have foiled many attacks but some are difficult to control."

On January 20 the Taliban launched the first of two massive attacks in Kabul: an hours-long assault on a luxury hotel in which at least 25 people were killed, including many foreigners.

One week later an ambulance laden with explosives detonated in a crowded street, killing more than 100 people and wounding hundreds more in one of the deadliest bomb blasts in Kabul in recent years.

The Taliban claimed responsibility, insisting the explosion had killed mainly police.

On Monday many residents awoke to the sounds of gunfire and explosions once more as IS militants attacked the battalion.

Relentless Taliban violence is not new to the city. But, analysts say, the insurgents' recent escalation is exacerbated by the lightning increase in IS attacks in the capital since 2016.

There is no reason to believe the Taliban and ISIS are partnering operationally, or conversely, competing to outdo each other, says Michael Kugelman of the Wilson Center in Washington, DC.

But "the cumulative effect of their attacks is simply devastating," he told AFP.