WASHINGTON - The United States issued a global travel alert over possible terrorist attacks Friday, one day after it announced the closure of some diplomatic missions in the Middle East and North Africa over the coming weekend.

"The Department of State alerts US citizens to the continued potential for terrorist attacks," the department said in a travel alert posted on its website.

The potential for terrorism was particularly acute in the Middle East and North Africa, with a possible attack occurring on or coming from the Arabian Peninsula, it added.

"Current information suggests that al-Qaida and affiliated organizations continue to plan terrorist attacks both in the region and beyond, and that they may focus efforts to conduct attacks in the period between now and the end of August," the State Department said.

A US flag flies in front of the Annex I building inside the compound of the US embassy in Baghdad in this Dec 14, 2011, file photo. [Photo/Agencies]

It warned of possible terrorist attacks on public transportation systems and other tourist infrastructure, adding that the United States is working closely with other nations on the threat.

In Manama, the US embassy to Bahrain said in an advisory that due to its closure on the coming Sunday, US citizen services and visa appointments have been rescheduled on an individual basis.

The embassy advised US citizens in the Gulf Arab nation to avoid areas of large gatherings, warning that "even demonstrations intended to be peaceful can turn confrontational and escalate into violence."

In Abu Dhabi, the US embassy to the United Arab Emirates said the closure of its office and the consulate general in Dubai is a "precautionary step" based on security concerns and instructions of the US State Department.

The embassy said it is possible that "we may have additional days of closings as well, depending on our analysis."

A total of 21 US embassies and consulates across the Muslim world will be closed through the weekend, in particular on Sunday, a workday in Muslim countries, after State Department spokeswoman Marie Harf warned of security and safety threats.

Harf told reporters on Thursday that the decision was taken "out of an abundance of caution and care for our employees and others who may be visiting our installations."

After the United States announced the temporary closure of some of its foreign missions, Britain said it will also close its embassy in Yemen on Sunday and Monday driven by "increased security concerns" as a precautionary measure.

The Foreign Office said in a statement that it has withdrawn a number of staff from Yemen and advised British nationals against all travel there as security situation was particularly concerned in the final days of Ramadan, the Muslim holy month which ends on Wednesday evening.

The statement did not mention any specific threats but said that the Foreign Office constantly reviewed the security of staff and its embassies.

Riot policemen stand guard during a protest to demand the release of Yemeni detainees in the prison of Guantanamo Bay, outside the US embassy in Sanaa in this June 17, 2013, file photo. [Photo/Agencies]

In Brussels, European Commission spokesman Alexandre Polack said the European Union would be taking "all necessary precautions" following the US announcement.

"We are aware of the move by the US and we are in contact with our US counterparts," Polack said. "Delegations of the EU in the affected region are liaising with US embassies."

Last year, the United States issued a warning cautioning its diplomatic facilities throughout the Muslim world of possible violence linked to the anniversary of the September 11 terrorist attacks in 2011.

Dozens of US foreign missions came under attack last September over a US-made movie that insulted Islam.

On Sept 11, 2012, US Ambassador to Libya Christopher Stevens and three other Americans were killed in one of such attacks in the country's eastern city of Benghazi.