U.S. officials denied a suspect was under arrest Wednesday in the deadly Boston Marathon bombings.

A law enforcement official briefed on the investigation told The Associated Press earlier in the day that a suspect was in custody. But the FBI and the U.S. attorney's office in Boston said no arrests had been made.

South Korea said on Wednesday it had agreed to buy a fleet of U.S. Apache attack helicopters in a deal with reported to be worth $1.5 billion, at a time of heightened tensions with the North.

The Defense Acquisition Program Administration (DAPA) said it would acquire 36 of the AH-64E Apache Guardian choppers from Boeing over a three-year period from 2016.

A huge earthquake that struck Iran's rural southeast region killed one woman and injured more than two dozen other people, media reports Wednesday cited officials as saying.

"A woman was killed by a mountain landslide following the quake," Alireza Shahraki, governor of Khash city, was quoted by ISNA news agency as saying.

An envelope addressed to a Republican senator tested positive Tuesday for ricin, a potentially fatal poison, congressional officials said, heightening concerns about terrorism a day after a bombing killed three and left more than 170 injured at the Boston Marathon.

One senator, Claire McCaskill of Missouri, said authorities have a suspect in the fast-moving ricin case, but she did not say if an arrest had been made. She added the letter was sent from an individual who frequently writes lawmakers.

The Pentagon has requested $220.3 million in 2014 to bolster Israel's "Iron Dome" missile defense system despite broader cuts to U.S. military spending, according to budget documents.

The U.S. Missile Defense Agency also is asking for an additional $175.9 million in fiscal year 2015 for Israel's homegrown missile defense network, according to the agency's budget proposal posted online.

U.S. Defense Secretary Chuck Hagel is due in Israel for an official visit on April 21 on his first trip to the region since taking over as Pentagon chief, an Israeli official confirmed to Agence France Presse on Tuesday.

According to the official, Hagel will be arriving "on Sunday" for "a short working visit."

The FBI's investigation into the bombings at the Boston Marathon was in full swing Tuesday, with authorities serving a warrant on a suburban Boston home and appealing for any private video, audio and still images of the blasts that killed three and wounded more than 170.

President Barack Obama said it was unclear whether the bombings were carried out by an international organization, domestic group or a "malevolent individual."

Saudi Arabia, the Gulf Cooperation Council and the Organization of Islamic Cooperation all condemned on Tuesday the twin bombings at the Boston Marathon, calling them an act of terrorism.

Three people were killed and more than 170 wounded in the bombings in the worst attack in the United States since the September 11, 2001 atrocities.

The United States on Monday condemned the deadly barrage of rockets fired by Syrian rebels into the Lebanese region of Hermel, which left two people dead and five others wounded on Sunday.

The U.S. State Department said it condemns attacks against Lebanese territory, whichever side they may come from.

Palestinian Prime Minister Salaam Fayyad resigned on Saturday, leaving the Palestinians without one of their most moderate and well-respected voices just as the U.S. is launching a new push for Mideast peace.

A statement from the official Palestinian news agency Wafa said President Mahmoud Abbas met with Fayyad late in the day and accepted his resignation, thanking him for his service. According to the statement, Abbas asked Fayyad to continue to serve in his post until Abbas forms a new government.