Iran says it targets US radar in Bahrain. What do we know?

The Bahrain Defence Force says its air defence systems thwart several Iranian 'aerial attacks'.

Iran's Islamic Revolutionary Guard Corps (IRGC) says it has launched six drones at a US air defence radar system at Bahrain's Riffa Air Base in response to what it describes as hostile US actions.

Sirens sounded in Bahrain on Sunday as its Ministry of Interior urged residents to "remain calm" and "proceed to the nearest safe location". It was the second time in three days that the IRGC claimed to have targeted a US radar system in Bahrain.

The US military said it intercepted two Iranian drones on Friday but has yet to comment on Sunday's claim.

Here is what we know:

What happened on Sunday?

The IRGC said it struck the radar at Bahrain's Riffa Air Base, according to a statement carried by the IRGC-affiliated Fars News Agency.

Bahrain's Interior Ministry issued two alerts within about three hours, the first about 4:30am (01:30 GMT). The ministry warned of a "potential threat" and urged residents to seek shelter. It gave no further details about the threat.

The Bahrain Defence Force also said its air defence systems thwarted several Iranian "aerial attacks" targeting the kingdom.

In its statement, the IRGC said the Strait of Hormuz remained closed and claimed that US efforts to escort ships through the waterway had failed. It warned that any US attack would draw a more severe response.

What happened in Bahrain on Friday?

The IRGC said on Friday that it destroyed a US early-warning radar system in Bahrain in retaliation for what it described as an air attack on a telecommunications tower in southern Iran. The US military's Central Command (CENTCOM) denied the claim, saying it had shot down two IRGC drones and there were no injuries or damage.

In a statement carried by Iran's semiofficial Tasnim News Agency, the IRGC called the operation a "serious warning" over what it described as aerial provocations and oil smuggling in the Strait of Hormuz. Reuters reported that Friday marked the first time since early September that Iran had claimed an attack on US military assets in a Gulf country.

Tehran has told the United Nations Security Council it would respond immediately to renewed US or Israeli attacks and has accused Bahrain and other Gulf states of supporting US military operations. Bahrain has called for the full implementation of Security Council Resolution 2817, which condemned Iranian attacks on Bahrain and other countries in the region and demanded they stop.

Manama, Bahrain, is where the US Navy's Fifth Fleet is based. A Pentagon inspector general's report released in September found that Iranian attacks had damaged or destroyed buildings at US installations in eight countries, including Bahrain, in the first four months of the US-Israel war on Iran, which began on February 28.

What has happened in the Strait of Hormuz?

The IRGC's navy said two oil tankers struck sea mines on Saturday while trying to pass through the Strait of Hormuz. In a statement carried by Iran's state news agency IRNA, it said the vessels had switched off their navigation and tracking systems and were using what it called an "unauthorised" route.

The IRGC said two other tankers turned back towards the Gulf after receiving warnings from its maritime traffic control centre.

Reporting from Tehran, Al Jazeera's Mohammed Vall said on Saturday that there were "two similar incidents yesterday" and the number of tankers hitting mines has increased.

Vall said Iran claims that the Strait of Hormuz is under its "full control" and "only Iran and Oman have the right to control it". The United States rejects that claim.

According to Vall, Iran blamed the incidents on the tanker owners and the countries backing them, saying they had failed to comply with the regulations Iran imposed on passage through the strait.

Where do efforts to end the war stand?

Diplomatic efforts to stop attacks and reopen the Strait of Hormuz remain stalled with Iran's parliamentary speaker and chief negotiator, Mohammad Bagher Ghalibaf, telling Al Jazeera that Tehran wanted to move beyond a state of "no war, no peace".

Ghalibaf said in the interview last week that Iran has conveyed seven conditions for a deal through a Qatari mediator and was awaiting an official US response. The conditions he outlined included lifting the US naval blockade and sanctions, releasing frozen Iranian funds, ending hostilities on all fronts and formally declaring the war over.

US President Donald Trump's administration, meanwhile, has tightened sanctions and maintained the blockade on Iranian ports.

Saeid Golkar, the UC Foundation associate professor of political science at the University of Tennessee at Chattanooga, told Al Jazeera that limited exchanges could escalate into a wider war.

"Both sides may prefer to avoid a full-scale war, but the danger lies in miscalculation," Golkar said.

"Iran may continue limited maritime and regional escalation to increase pressure while Washington could respond militarily. Such exchanges could eventually lead to a broader conflict that neither side initially intended."