Interpol has issued a global security alert following a series of al-Qaida-linked prison breakouts in which hundreds of terrorists escaped.

The warning came a day after the US state department issued a worldwide travel warning to American citizens and closed 21 of its embassies over intelligence suggesting that the terrorist network was planning attacks during August. Britain is closing its embassy in Yemen for two days due to increased security concerns.

In a statement issued from its headquarters in Lyon, France, Interpol urged countries around the world to show "increased vigilance", following prison breakouts over the past month in nine countries, including Iraq, Libya and Pakistan.

"With suspected al-Qaida involvement in several of the breakouts which led to the escape of hundreds of terrorists and other criminals, the Interpol alert requests the organisation's 190 member countries' assistance in order to determine whether any of these recent events are co-ordinated or linked," the international police agency said.

"Interpol is asking its member countries to closely follow and swiftly process any information linked to these events and the escaped prisoners. They are also requested to alert the relevant member country and Interpol general secretariat headquarters if any escaped terrorist is located or intelligence developed which could help prevent another terrorist attack."

Prison breakouts took place in Pakistan on 31 July in a Taliban-led operation, and in Iraq at the Abu Ghraib prison overnight on 22 July. Some 500 convicts, among them senior al-Qaida operatives, escaped from Abu Ghraib. More than 1,100 inmates broke out of a prison on the outskirts of Benghazi on 27 July.

British authorities have not yet specified the nature of the threat which led to the decision to close the embassy in the Yemeni capital of Sana'a on Sunday and Monday in what was described as "a precautionary measure". A Foreign Office spokesman would not say if the closure was due to a specific threat.

British nationals have been warned against all travel to Yemen, and those in the country have been advised to leave immediately, as it was "extremely unlikely" that their evacuation could be arranged if the security situation deteriorated.

The Foreign Office recommended particular vigilance during the Muslim holy month of Ramadan, which ends on 8 August, when "tensions could be heightened".

Yemen has become a stronghold of al-Qaida over recent years – with the local offshoot, al-Qaida in the Arabian Peninsula, believed to have several hundred members – despite efforts by the country's authorities to suppress the group and US drones killing leaders, including Anwar al-Awlaki. Yemen was the source of an attempt to bomb a US-bound airliner in 2009.

There has been unrest recently after the mutiny of troops in the Republican Guard and fighting around the presidential palace on Friday.

The US embassy in Yemen is one of 21 which will be closed on Sunday following the state department's warning of the "continued potential for terrorist attacks, particularly in the Middle East and north Africa, and possibly occurring in or emanating from the Arabian peninsula".

The global travel warning to US citizens said: "Current information suggests that al-Qaida and affiliated organisations 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 alert warned of "the potential for terrorists to attack public transportation systems and other tourist infrastructure".

Explaining the embassy closures, a state department spokeswoman said: "The department has been apprised of information that – out of an abundance of caution and care for our employees and others who may be visiting our installations – indicates we should institute these precautionary steps. The department, when conditions warrant, takes steps like this to balance our continued operations with security and safety."

On 7 August it is the 15th anniversary of the bombing of US embassies in Tanzania and Kenya, which killed hundreds of people and brought the late al-Qaida mastermind, Osama bin Laden, to public attention for the first time.