NAIROBI, Oct. 2 (Xinhua) -- Kenyan police said on Tuesday they have stepped up security surveillance across the country following intelligence reports that Somali militants were planning to carry out retaliatory terror attacks in the East African nation.

Police Spokesman Eric Kiraithe told journalists in Nairobi that security forces have increased surveillance measures in key installations, private and public places and urged the public to exercise caution while dealing with people with ulterior motives.

"We have received intelligence report that the Al-Shabaab and their sympathisers are planning a retaliatory attack after the capture of Kismayo city by the Kenya Defence Forces (KDF)," Kiraithe told journalists in Nairobi.

Bomb attacks using improvised explosive devices and grenades have become more frequent in the capital Nairobi, the coastal city of Mombasa and northern eastern region since KDF entered Somalia last year to secure the shared border with the lawless country.

Police have particularly warned against the laxity in the screening of cars for explosives at all shopping malls and any business or social gatherings with at least 10 people at any given moment that these might be vulnerable to attacks.

Bomb attacks using improvised explosive devices and grenades have become more frequent in the capital Nairobi, the coastal city of Mombasa and northern eastern region since KDF entered Somalia last year to secure the shared border with the lawless country.

Kiraithe said security had been stepped up and appealed to city residents to be extra vigilant and take security measures seriously, regardless of their status in society.

"The intelligence report shows a change of tactics by the Al- Shabaab as they are now using women for suicide by bombing. The police are now urging Kenyans to be cautious especially in hotels, supermarkets, in public Service vehicles as well as populated residential areas," he said.

Two policemen including a 9-year-old child were killed on Friday evening and Sunday morning respectively in suspected retaliatory attacks by the militants who have been forced out of the strategic port city of Kismayo.

Even though no one has claimed responsibility, the authorities suspect it's the work of the Somalia insurgents who have been hurling bomb and grenade attacks in Kenya.

"We have heightened security surveillance to ensure the country is safe. We wish to inform all Kenyans that police and other security agencies are doing all that can be done to make the country safe," he said.

The East African nation has warned that attacks as threatened by the Somali-based terrorist group Al-Shabaab could affect the country's risk profile limiting the number of new investments being made especially by foreign investors.

Attacks could further affect the number of tourism visitors affecting the planned attraction of two million tourists targeted for this year compared to 1.6 million tourists that visited last year.

Already, some European countries and the United States have issued travel warning for their citizens visiting Kenya, which has led reduction in the number of tourists visiting the country.

Tourism is one of the main drivers of economic growth and earns Kenya over 1 billion U.S. dollars and provides employment to thousands of its citizens.

The attacks also slow the pace of doing business locally as local investors avoid or postpone none essential activities.

Security officers are patrolling all the avenues in the capital, including the backstreets, which have bore the brunt of terror attacks.

Terrorists have struck on the streets frequented by hundreds of people several times, killing several people and injuring scores others.

Kiraithe called on hotels, landlords and public service vehicles to always endeavor to establish the identity of their customers by examining their identification documents.

In case of the national Identity Card, Kiraithe said those responsible should check the names, date of birth, place of issue, date of issue, district of origin, Division, Location and sub- location. "In case of a Passport, in addition to the above details, ascertain nationality, date of issue, place of issue and expiry date," he said.

The police spokesman said all police officers have been sensitized to be alert at all times and be ready to thwart any attempts by terrorizes to inflict suffering on Kenyans.