-LRB- CNN -RRB- -- The U.S. Embassy in Yemen , which was closed over the weekend because of security concerns , reopened Tuesday , a day after Yemeni forces conducted successful security operations . A statement posted on the embassy 's Web site said `` successful counter-terrorism operations '' conducted by Yemeni security forces on Monday , north of the Yemeni capital , Sanaa , addressed `` a specific area of concern and have contributed to the Embassy 's decision to resume operations . '' Yemen 's state-run news agency , SABA , reported Monday that two al Qaeda suspects were killed and two others were injured in clashes with a Yemeni anti-terrorism unit However , Mohamed Ahmed al-Haniq , the al Qaeda unit 's leader , and an unknown number of his `` companions '' were able to escape during the clashes , SABA reported , citing Yemen 's Interior Ministry . The U.S. Embassy said the threat of terrorist attacks against American interests in Yemen `` remains high , '' and it urged American citizens in the country `` to be vigilant and take prudent security measures . '' Yemen fertile ground for terror groups A senior State Department official , who did not want to speak on the record because of the sensitive nature of the information , said Yemeni authorities have helped the United States with additional security precautions at the embassy site . The United States ' decision to close its embassy came after intelligence suggested that four al Qaeda operatives were planning an attack on the compound , a senior administration official said Monday . The official said the United States had information that a group of eight terrorists had been planning an attack . Yemeni forces killed three in recent days and another was captured wearing a suicide vest , but the other four were believed to be at large , the official said . It was not immediately clear if the same al Qaeda members in Monday 's clashes were among the group of eight suspected terrorists . U.S. lawmakers have highlighted what they say are the threats posed by terrorists in Yemen . `` As we commit ourselves to the fight in Afghanistan , some of the what I 'll call the enemy forces , the extremist forces , move to new bases of operation such as Yemen , from which they strike us , '' said Sen. Joe Lieberman , I-Connecticut , at a news conference with Sen. John McCain in Iraq Tuesday . `` I 've been quoting something that was said to us by an American working in Yemen when Sen. McCain and I visited in August , which was perhaps a bit overstated but it makes a point . He said to me : ` Iraq was yesterday 's war . Afghanistan is today 's war . And if we do not act preemptively now , Yemen will be tomorrow 's war . ' '' McCain noted that on the visit he had a `` very strong impression '' about the nation 's difficulties , particularly the presence of al Qaeda . `` The government of Yemen is going to need our help in combatting al Qaeda , '' McCain , R-Arizona , said . `` There needs to be significant effort made in improving their economy , and we can not allow Yemen to be a base for al Qaeda to mount attacks on other countries in the region as well as the U.S. '' On Monday , U.S. Secretary of State Hillary Clinton called the situation in Yemen a possible threat to regional and global security , but commended Yemen for taking action against al Qaeda networks . The United States and Britain closed their embassies Sunday . Britain 's Foreign Office also cited security concerns and its embassy remained closed Tuesday . `` The British Embassy in Yemen will remain closed to the public today , '' a statement from the embassy said . `` Some embassy personnel will be in and whoever needs to contact the embassy can do it via the phone or e-mail but people wo n't be able to walk into the embassy . '' Several other nations also made changes at their Yemen-based embassies Monday , including Japan , France , Spain and Germany . Each cited the need for increased security measures . France closed its embassy to the public , although French Foreign Ministry spokesman Bernard Valero said Tuesday that embassy employees will continue their work . Valero said the embassy will reopen once work to secure the site , already in progress before the latest threat , is finished . Spain also restricted public access to its embassy , the Spanish Foreign Ministry said , adding that the embassy continued to function `` normally . '' Japan halted service at the consulate section of its embassy . The Japanese Foreign Ministry said the decision was based on the threat of terror , not a specific threat . Germany said that while its embassy remained fully operational , security measures were increased . The German Foreign Ministry said fewer visitors were allowed into the embassy compound . The wave of concerns follow last month 's alleged attempted terrorist attack by a Nigerian man who boarded a flight in Amsterdam , Netherlands , and allegedly tried to detonate explosives hidden in his underwear as the flight approached Detroit , Michigan . The attempt failed , and other passengers and crew grabbed the suspect . The Yemen-based al Qaeda in the Arabian Peninsula claimed responsibility for the Christmas Day plot . U.S. President Barack Obama has also linked the suspect , Umar Farouk AbdulMutallab , to the group , which is a combination of al Qaeda networks in Saudi Arabia and Yemen . The AQAP group in Yemen has said that the attempted attack on the airliner was in retaliation for airstrikes against it on December 17 and 24 . However , Yemen has said that AbdulMutallab purchased his ticket on December 16 . The U.S. Embassy in Yemen has come under attack numerous times in recent years . In September 2008 , 10 people were killed -- among them police and civilians , but no embassy employees -- when insurgents opened fire and set off explosions outside the compound .