NAIROBI - The United States has issued a fresh travel advisory, warning its citizens in Kenya to assess their personal security situation in the wake of increased sporadic grenade attacks in the East African nation.

In its updated Travel Advisory, the State Department said levels of risks vary throughout the country, saying many of the perpetrators of terror threats still remain at large and still operate in the East Africa region.

"The US Department of State warns US citizens of the risks of travel to Kenya. US Citizens in Kenya and those considering travel to Kenya should evaluate their personal security situation in light of continuing and recently heightened threats from terrorism and the high rate of violence crime in some areas," it said.

In its latest warning, Washington said the US embassy in Nairobi has limited official American government travel to the East African nation until the security situation improves.

"The Embassy will continue to monitor the security situation and provide updates. This replaces the Travel Warning of April 4 to update information about the current security situation," it said.

The warning says America has continued to receive information about potential terrorism threats aimed at US, Western, and Kenyan interests in the country.

"Terrorist acts can include suicide operations, bombings, kidnappings, attacks on civil aviation, and attacks on maritime vessels in or near Kenyan ports," the warning said.

Washington had warned its citizens on June 23 of an impending terrorism attack in Kenya's coastal city of Mombasa and ordered Americans to vacate Mombasa as it also suspended all US government travel to the port city until July 1, over terrorism fears.

A blast occurred the following day in the port city when terrorists threw grenades into at a bar in Mombasa, where patrons were gathered to watch the European championship soccer match between England and Italy, killing at least three people and left 25 others injured.

The June 24 attack came hours after Nairobi bitterly protested at the decision by US government to issue, terming an act of economic sabotage.

Mombasa, the country's second largest city and a major tourist spot is one of various cities targeted by a series of grenade attacks and abduction of foreigners in recent months.

Kenyan authorities 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.

Kenya's tourism has suffered a decline the number of tourists arriving since September 2011 when the Somali militant group, the Al-Shabaab, carried out the kidnappings of tourists in the Lamu archipelago and the kidnapping of the Spanish volunteers.

The port city, the capital Nairobi and other parts of Kenya have suffered a series of grenade attacks since Kenya sent troops into Somalia last year to try to pursue Al-Shabaab insurgents it blames for a surge in violence and kidnappings threatening tourism.