Arab capitals are expecting further violent clashes after the killing of three demonstrators in the Gulf state of Bahrain, and the reported death of 15 people in violence in Libya, threatened an escalation of regional unrest in the wake of the popular uprisings in Egypt and Tunisia.

Fresh protests are expected today after Friday prayers in Manama, the capital of Bahrain, in Cairo (in celebration of Hosni Mubarak's departure a week ago), and in Sana'a, capital of the Yemen, and perhaps elsewhere.

Britain announced a review of licences granted for arms exports to Bahrain which it would "urgently revoke" if the sales criteria had been breached in their use, after it emerged that types of crowd-control weapons similar to those used in the crackdown were supplied by British companies. Despite concerns among activists over Bahrain's rights record, British firms were last year granted licences, entirely unopposed, to export crowd-control weapons that can lead to fatalities in use.

Meanwhile the US secretary of state, Hillary Clinton, telephoned her Bahraini counterpart to express "deep concern" after riot police stormed a protest camp in central Manama, killing three people in what the opposition called a "massacre".

Bahrain is situated in the Gulf near Iran and is home to the US Fifth Fleet and also to the UK command which supports Royal Navy warships in the region. The island has a history of volatility because its Shia Muslim majority is ruled by a Sunni monarchy. William Hague, the foreign secretary, told MPs: "We have conveyed our concern about these events and the level of violence."

Last night Egyptian authorities arrested the former interior minister, Habib el-Adly, and two other former ministers who are under investigation for corruption, security officials said.

Authorities also arrested steel tycoon Ahmed Ezz, once a prominent member of the ouster leader Hosni Mubarak's ruling National Democratic party.

Saudi Arabia and other Gulf states signalled their alarm at the unprecedented regional unrest at a meeting of foreign ministers held in Manama.

The sectarian aspect of Bahrain's violence could add to discontent among the Shia minority in oil-producing areas of east Saudi Arabia, which is linked to the island state by a 15-mile causeway.

Bahrain's anti-government protesters vowed to avenge three of their number who had been killed by riot police. Demonstrators spent the day regrouping inside the grounds of a hospital after being ousted from their nearby camp on the Pearl Roundabout in the capital's centre by up to 500 officers who attacked shortly after 3.15am local time. Their numbers rose to 4,000 by late afternoon, and plans for a rally on Friday were in full swing.

At least 300 people were wounded in the assault, several dozen seriously. A trauma surgeon from Salmaniya hospital was in an intensive care ward after being attacked at the roundabout camp, then handcuffed and repeatedly kicked in the head.

Bahrain's interior ministry produced images that it said were of police officers recovering from knife wounds and beatings that they had received during the clashes. The claim were denied by the protesters who said they had had no weapons and were attacked as they slept. Doctors were leading the calls for revolt, with an overwhelmingly Shia audience urging them on in front of the hospital as they chanted anti-regime slogans. Several doctors and surgeons were at one stage hoisted on to shoulders and given loudhailers, which they used to urge demonstrators to take to the streets again.

Bahrain's foreign minister was due to give a statement after saying earlier in the week that the deaths of two protesters on Monday and Tuesday was "catastrophic" for the regime. That caused palpable resentment among the hordes of demonstrators who sat vigil outside the hospital and morgue following the casualties.

Bahraini demonstrators say they want constitutional democracy, the release of political prisoners, more jobs and housing, and removal of the prime minister, Sheikh Khalifa bin Salman Al Khalifa, the king's uncle, who has been in office for 40 years.

According to the Foreign Office's records and the Campaign Against the Arms Trade, the UK has supplied Libya with similar weapons and ammunition to those sold to Bahrain.