The recent arrest of two Iranians in Kenya on suspicion of plotting bomb attacks has heightened fears that Tehran is widening its covert war against Israel and the United States as Washington expands its secret intelligence operations across Africa.

The Iranians have rarely mounted major covert or intelligence operations in Africa, although they have used Sudan as a key conduit for weapons destined for the Palestinian Hamas militants and their allies in the Gaza Strip in recent years.

But West Africa and the Horn of Africa have largely been operational areas for al-Qaida, a Sunni organization that's religiously and ideologically opposed to Shiite Iran, and its Somali offshoot, al-Shabaab.

Kenya security authorities, aided by U.S. and British agents, arrested the two Iranians June 20 in Nairobi, the West African country's capital. The men reportedly led authorities to a cache of 33 pounds of military-grade explosive, believed to be RDX.

They were charged Monday with intent to carry out bombings, which they deny. But the U.S. Embassy in Nairobi issued a warning Tuesday to Americans to avoid traveling to Kenya.

The arrest of the Iranians suggests that "the suspects may have been preparing to deliver the next blow in the covert intelligence war that has raged since 2007 between the United States, Israel and their allies on one side and Iran and its allies on the other," the U.S. global security consultancy Stratfor observed.

Most of the attacks carried out by Sunni militants, such as al-Shabaab, have been small improvised explosive devices or hand grenades, although al-Shabaab killed some 70 people in two major bombings in Kampala, capital of Uganda, in October 2010.

"This latest plot diverges from the normal Islamist activity and more closely resembles the strong of Iranian attacks and attempted attacks against Israeli interests in multiple countries," Stratfor noted.

The U.S. Embassy in Nairobi has not lifted the travel warning. That suggests "the two individuals are not the full extent of the threat," Stratfor commented.

The relatively small amount of RDX found at a cache in the Kenyan port city of Mombasa on the Indian Ocean was not enough for a major bombing, but ample for the kind of recent anti-personnel attacks against Israelis in Azerbaijan, India and Thailand.

Iran has in recent years plotted several attacks against Israelis in Azerbaijan, its northern Muslim neighbor and a former Soviet republic that has close military and intelligence ties with Israel and the United States.

In February, Iranian agents have carried out bombings or attempted attacks against Israelis in India, Georgia and Thailand.

On Monday, a Malaysian court ordered the extradition to Thailand of Masoud Sedaghat Zadeh, 31, to face charges related to Feb. 14 bombings in Bangkok.

These attacks have been mounted to retaliate for U.S. and Israeli covert operations targeting Iran's nuclear project. These include cyberattacks on its uranium enrichment program and assassinating scientists engaged in the highly secret program.

A multinational investigation of these bomb plots has, as London's Guardian newspaper reported, "produced the clearest evidence yet that Iran was involved, illustrating the risks to the West if it fails to reach detente with Tehran over its nuclear weapons program."

The third round of talks between U.S.-led powers and Iran collapsed in Moscow June 19, and the prospect of further negotiations now seem dim while the U.S. military buildup in the Persian Gulf continues.

Indian security officials say a February bomb attack that badly wounded the wife of the Israeli defense attache in New Delhi, was the work of an Iranian "security entity."

At least 10 Iranians were identified in the Indian operation, funded by money transfers from Tehran.

U.S. and British intelligence sources say the attacks in India and Thailand were first plotted in April 2011, with at least five people involved in surveillance missions to both countries.

But that fall, the plotters had established safe houses, local support networks, finances and detailed surveillance of the targets, these sources reported.

It's not clear at this stage whether a similar set-up was organized in Kenya.

It's possible Iranian intelligence has utilized the large Lebanese Shiite community in West Africa, which is mainly involved in the diamond trade and, more recently, arms smuggling.

U.S. officials say these Shiites are closely linked to Hezbollah, often used by Tehran on foreign operations.