Gunfire erupted in a Shia town in Saudi Arabia on Wednesday after police sealed it off with armoured vehicles, a resident said.

Awamiya, near Dammam on the Gulf coast, has been the scene of repeated incidents since protests by the minority Shia community began in 2011.

The resident said he saw black smoke rising over farms in the community of about 30,000 people when police moved in mid-afternoon.

"It was seen in all Awamiya," he said, describing how black armoured vehicles had sealed off the area.

He added that he heard heavy, periodic gunfire but could not see who was shooting.

"Saudi forces raided Awamiya, some farms," he told AFP, adding that there was no word on arrests or casualties.

The interior ministry made no immediate comment.

A local source told Middle East Eye that security forces were looking for "wanted people".

In April, the ministry said a policeman died in a gunfight with "terrorists" in Awamiya.

That followed the arrest there in January of one of 23 people on a wanted list issued after the earlier protests and violence in Eastern Province.

Many others on the list had been already detained or killed in shootouts.

Most Saudi Shia live in the oil-rich east, and many complain of marginalisation.

Activists say several Shia have been sentenced to death since the protests.

These include Nimr al-Nimr, a Shia religious leader, and his nephew, Ali al-Nimr, who was only 17 at the time of his arrest.

The Berlin-based European Saudi Organisation for Human Rights said on Tuesday that a second youth, Dawoud al-Marhoon, had, like Ali al-Nimr, exhausted all court appeals of his death sentence.

On Wednesday, Saudia Arabia's embassy in the UK released a short statement condemning foreign "interference" over the execution of Nimr.

"The judiciary is an independent body and the Kingdom of Saudi Arabia rejects any form of interference in its internal affairs and any impingement on its sovereignty or the independence and impartiality of its judiciary," the statement said.

Marhoon was also 17 when he was arrested, the rights group said.

Executions cannot be carried out without the final approval of King Salman.

A number of prominent commentators condemned the terseness of the statement on Twitter: