Nairobi on Wednesday canceled an oil import deal with Iran that would have broken U.S. and EU embargoes after international pressure, officials said Wednesday.

"It has been canceled - although effectively we never signed any agreement with the Iranian government, what we had was a memorandum of understanding with Iran," the energy ministry's permanent secretary Patrick Nyoike told Agence France Presse.

Four foreign aid workers kidnapped in Kenya's Dadaab refugee camp were released overnight in southern Somalia after a short gunfight, and were safe with the Kenyan army, officials said Monday.

"They are safe in our hands, they have been freed," Kenyan army spokesman Cyrus Oguna told Agence France Presse, adding that the two men and two women seized on Friday were released after a joint operation of Kenyan and Somali troops.

The Vatican on Sunday termed twin attacks on two Kenyan churches which killed at least 17 people a "horrible and very worrying" act.

"The bloody attacks in Kenya in the town of Garissa against two churches, including a Catholic cathedral, during Sunday prayers, are a horrible and very worrying fact," spokesman Federico Lombardi told Vatican Radio.

Gunmen killed 10 people and wounded dozens when they opened fire and hurled grenades into two churches in the eastern Kenyan town of Garissa on Sunday, the latest in a string of attacks, police said.

Gunmen burst into the churches in apparently coordinated attacks targeting worshippers as they held Sunday prayer services in Garissa, some 140 kilometers (85 miles) from the border with war-torn Somalia. The attackers later escaped.

Gunmen killed at least one person and kidnapped an aid worker in Kenya's Dadaab refugee camp, close to the border with war-torn Somalia, police sources and the Red Cross said Friday.

The death toll from a grenade attack on a bar in the Kenyan city of Mombasa rose to three Monday, dealing a fresh blow to the government's efforts to secure the country and revive tourism.

The latest in a string of such attacks in the east African nation was likely to be blamed on Somalia's Islamist Shebab rebels and came after specific foreign warnings on travel to the resort town were pooh-pooed by Kenya.

The identities of two Iranians whose arrest in Kenya this week preceded a U.S. alert of a planned "terrorist attack" in the country are not yet known, authorities in Tehran said on Saturday.

"The identities of these persons are not yet known to us and the Iranian embassy in Nairobi is seeking to obtain information and a consular visit," foreign ministry spokesman Ramin Mehmanparast said, quoted by state news agency IRNA.

Two police officers were wounded Saturday in a blast, possibly caused by an improvised explosive device, in Kenya's Mandera region on the border with Somalia, police said.

"The officers were sheltering under a tree when the explosion went off, wounding both of them," said a senior police officer in Mandera.

A German national of Turkish origin wanted by Kenya for suspected links to Somalia's Islamist rebel group Shebab has been arrested in Tanzania, police in both countries said Wednesday.

"Yes, we have arrested him. He is now in Dar es Salaam where we are interrogating him," a senior Tanzanian police officer said, asking not to be identified.

Kenyan Internal Security Minister George Saitoti was killed on Sunday alongside a junior minister and four others after a police helicopter crashed near Nairobi, the vice-president said.

"It is unfortunate that we have lost honorable Prof Saitoti, assistant minister Orwa Ojode," Kalonzo Musyoka told journalists.