Kenya's Westgate shopping mall, the site of a deadly attack in which 67 people were killed and scores were injured in 2013, has reopened.

Security was tight around the mall as shop owners opened their businesses on Saturday for the first time since the attack.

The mall has installed x-ray machines, explosive detectors and bullet-proof guard towers.

Gunmen from the Somalia-based armed group al-Shabab stormed the popular mall on September 21, 2013, in a brazen attack that the group said was in retaliation for Kenya's military operations in Somalia.

Kenyan troops were locked in a firefight with the gunmen in a siege that lasted for three days.

Nadia Osman, who is reopening a shop in the mall called the Fragrance Lounge, told Al Jazeera that she was at the mall when the al-Shabab attack took place.

"I ran out in a very bad state. It was the worst day ever. I had to come into the mall after a few weeks to recover the stock," Osman said.

"We're ready to open, we're ready to sell but are people going to come in?

"We urge everyone to support us. It could happen anywhere, any time. The security is much better than where we were, we are much better than where we were two years back but I feel we still have a way to go."

Al-Shabab has since claimed a string of attacks in Kenya, with the deadliest in April this year, when its gunmen killed 148 people at Garissa University in the country's east.

The reopening of the Israeli-owned mall came just a week before US President Barack Obama visits Nairobi - a sign, according to the city's governor, that the capital was safe.

Nairobi Governor, Evans Kidero, said security had been improved around the city.

"We are happy that we could have been hurt but our spirits have not been broken, it is a demonstration of the determination and the positiveness and the resilience and the indomitable spirit of the Kenyan people so we are back," he said.