Getting into buildings, office and shopping complexes in Kenyan capital Nairobi has become a little harder as security is beefed up following a terror attack at the upscale dusitD2 Hotel in the expatriate district of Westlands.

Kenyan police confirmed that 21 people were killed and dozen others injured in the terrorist attack by Somali militant group al-Shabab.

While some of the business premises have added more security guards, others have enhanced surveillance and security checks to ensure criminals have little chance to get in.

Vehicles are being checked thoroughly unlike in the past weeks as individuals are also frisked, with some buildings allowing in only those who produce National Identity Cards while others asking visitors to leave their luggage at the entrance.

Idling around buildings, a common practice in Nairobi as most of them are reference points for those who want to meet, is now being discouraged, and so is the parking of vehicles at undesignated places near the buildings.

There is certainly a new security order in the capital Nairobi and citizens are feeling it as companies don't want to take chances following the terror attack.

At the Nation Center, one of the iconic buildings in the city and popular meeting point for city residents, the number of security guards has been added both at the entrance and around the building, with the management discouraging idling.

"Please move away from here. We do not encourage holding of informal meetings around this place," a security guard told a group of four young men who were engaging in banter on Saturday.

Before the attacks, most supermarkets in the capital Nairobi were allowing their customers to get in with bags after being frisked, which they will pack in goods bought following a national ban on plastic bags.

But since Tuesday, a number of supermarkets have become strict, with customers asked to leave anything they are carrying at the luggage section before getting in.

"Leave the bag here," a security guard ordered a customer at one of the branches of Tuskys Supermarket on Saturday.

"You will come for it after paying for the goods and put them in," he added as the male customer's protests fell on deaf ears.

Kenyans have welcomed the new security measures, noting that they would help keep terrorists at bay.

"I am impressed by the increased security checks at buildings in Nairobi but I hope they would last because initially they have been enforced for about two weeks after a terror attack and then forgotten until the next incident," said Moses Njenga, a primary school teacher in Nairobi.

However, some are skeptical if the measures would really deter terrorists and called for a better strategy to deal with the crime.

"There was a working security check at the dusitD2 hotel yet it did not stop the terrorists from getting in. We need to rethink of a better way of stopping terror activities from being planned," said banker Tina Kimonge.

Kenya on Friday announced that in six months' time, it would issue private security guards manning malls, banks, supermarkets and even some residential areas with guns to curb terrorist attacks.

Private Security Regulatory Authority director Fazul Mohamed noted that the guards are usually the first point of contact with the criminals in case of a terror attack, therefore, they must be equipped to respond appropriately.

"The selected security guards will also be taken through counter-terrorism training," he said.

After the atack, the East African nation is believed to be dealing with an even more complex problem of radicalization, with experts calling for empowerment of youth to help stem the vice.

"We must all engage them - the government, religious entities, corporates, community leaders and families. We can no longer be casual, security alertness is crucial," said James Ole Kiyiapi, a former permanent secretary of the Ministry of Education.