Sixteen people have died and three more are missing in Saudi Arabia after downpours caused flash floods in several areas of the desert kingdom, the civil defense authorities said on Wednesday.

Two others died in flash floods in neighboring Oman, local media reported, as cloudbursts swept across most Gulf countries.

Saudi police arrested an activist wanted on security-related charges after a gunfight in the kingdom's Eastern province, scene to sporadic protests since early 2011, the interior ministry said.

Abdullah al-Asreeh, one of 23 activists on a wanted list for allegedly fomenting trouble in the eastern region, was arrested along with an unarmed man who faces charges of selling drugs and alcohol, the ministry said late Monday.

U.S. Defense Secretary Chuck Hagel arrived in Riyadh Tuesday to seal a major arms deal that will provide the Saudi kingdom with sophisticated missiles for its American-made fighter jets.

Hagel flew in from Jordan after a three-day visit to Israel in his first tour of the region since he took office two months ago.

The Saudi Shura Consultative Council agreed on Monday to study a recommendation to switch the Islamic weekend in the kingdom to Friday and Saturday, like other Gulf states, state news agency SPA reported.

The weekend in Saudi Arabia remains on Thursday and Friday, although other Gulf states have pushed it back by one day to reduce the difference with the rest of the world, which affects financial markets and businesses.

Saudi authorities on Monday beheaded a citizen convicted of murder, the interior ministry said, bringing to 35 the number of executions in the kingdom so far this year.

Mohammad ben Ali al-Alawi was convicted of knifing a fellow citizen to death during a fight, the ministry said in a statement carried by the official SPA news agency, without giving further details.

A special anti-terror court has sentenced three Saudis to six years in jail each for a plot to kill U.S. nationals at the height of a campaign of al-Qaida attacks in the kingdom between 2003 and 2006, a witness said.

The court in Riyadh issued its ruling late on Sunday, said a witness at the hearing during which two other men were acquitted.

The Saudi deputy defense minister, Prince Khaled bin Sultan bin Abdul Aziz who played a key role in the 1991 Gulf War over Kuwait, has been dismissed, state news agency SPA reported Saturday.

The move is the latest in a reshuffle of princes holding government posts in the OPEC kingpin where the monarch's age and frequent hospitalization have raised concerns over its future leadership.

The United States unveiled plans Friday to sell $10 billion worth of advanced missiles and aircraft to Israel, the United Arab Emirates and Saudi Arabia in a bid to counter the threat posed by Iran.

It was highly unusual for the Pentagon to announce an arms deal covering three countries and the move seemed to be designed to send a warning to Iran that Washington's partners in the region were beefing up their military power.

Saudi Arabia is hoping to wean jailed al-Qaida militants off religious extremism with counseling, spa treatments and plenty of exercise at a luxury rehabilitation center in Riyadh.

In between sessions with counselors and talks on religion, prisoners will be able to relax in the center’s facilities which include an Olympic-size indoor swimming pool, a sauna, a gym and a television hall.

Saudi Ambassador Ali Awadh Asiri revealed on Thursday that political differences between Riyadh and Hizbullah were natural and should be used in Lebanon's national interest.

In remarks to As Safir daily, Asiri said that he was in continuous contact with Hizbullah. But stressed that their dispute on some political issues “were not a problem.”