NAIROBI - Kenyan authorities have made more arrests in connection with last Tuesday's terrorist attack in Nairobi. Meanwhile, Kenyan officials are vowing to prevent further attacks.

Kenya's top security agencies met in the coastal city of Mombasa to discuss ways to improve security and prevent attacks by militant group al-Shabab. The Islamist extremist group claimed responsibility for the attack on the Dusit D2 hotel and office complex that killed at least 21 civilians.

Speaking at the conference, Interior Minister Fred Matiangi said Kenyan forces are ready to repulse any attack.

"We are alert, and we remain alert 24/7. We are on duty 24/7 to serve our people to ensure that our country remains secure and safe. And anyone who bets on attempting to disrupting our peace got some answers last week, and they will get many answers if they try as we get along."

Kenyan officials say police and army troops killed all five gunmen who attacked the Dusit complex.

ì¼ë ëì´ë¡ë¹ ëì¬ìì í­í ê³µê²©ì´ Fire and smoke rises from an explosion in Nairobi, Kenya, Jan. 15, 2019. Fire and smoke rises from an explosion in Nairobi, Kenya, Jan. 15, 2019.

Since then, authorities have arrested at least 11 people in connection with the attack, including four suspects who surrendered to police Monday in the eastern town of Isiolo. Dozens more have been brought in for questioning.

Authorities acknowledge that al-Shabab continues to pose a threat.

A sub-county police commander Garissa County, Aaron Ombeo, said security officers stopped a suspected terrorist attack on a construction site.

"Unfortunately, as they were attempting to get to the premises they shot at a female. She is stable, she is undergoing treatment at Garissa. Security officers were guarding the facility, they had to respond to the extent the attackers fled to an unknown destination. We are still out there looking for the attackers," said Ombeo.

Nairobi based security expert Richard Tuta said al-Shabab is taking advantage of Kenya's political freedoms to operate. He said the country needs to strike a balance between freedom and national security.

Kenyan security forces help people to escape after Kenyan security forces help people to escape after a bomb blast at DusitD2 hotel in Nairobi, Kenya, Jan. 15, 2019. Kenyan security forces help people to escape after a bomb blast at DusitD2 hotel in Nairobi, Kenya, Jan. 15, 2019.

"The moment you hear a country being an open political system, it is a fact that some aspect of fundamental human rights are so much respected, including but not limited to the fact that [there is] a right to privacy. And the moment there is aspect of privacy, freedom of media, they serve as a conducive enabling environment for the operation of a terrorist organization," he said.

Kenya continues to be on high alert, and security has been heightened in areas where al-Shabab is suspected to be recruiting youth and might have sleeper cells.