Twin attacks on Western targets in Yemen's capital, Sanaa, have left one person dead and at least four injured.
Militants fired a rocket-propelled grenade at a British embassy car, slightly injuring one staff member as well as bystanders, officials said.
In the other incident a security guard at an Austrian gas company near Sanaa opened fire killing a French contractor and badly injuring a UK contractor.
Yemen has seen a string of militant attacks on Western targets.
The armoured UK embassy car was said to have been carrying the deputy chief of the British mission in Yemen when it was hit by shrapnel from the blast.
In a statement, the UK Foreign Office said the attack happened at about 0815 local time (0515 GMT).
"The vehicle was on its way to the British embassy with five embassy staff on board," the statement said.
"One member of staff suffered minor injuries and is undergoing treatment, all others were unhurt. We are informing their families at the moment. We are aware of at least two bystanders injured during the attack, and are seeking further details."
UK Foreign Secretary William Hague described the attack as "shameful".
"This morning's attack... highlights the risks our diplomats face working for Britain's interests abroad," he said.
"I am full of admiration for the way our embassy is dealing with this difficult situation.
"This shameful attack on British diplomats will only redouble Britain's determination to work with the government of Yemen to help address the challenges that country faces."
Yemen's Foreign Minister Abu Bakr Al Qirbi had promised "a vigorous investigation" into the attack, a Foreign Office spokesman said.
Yemen's President Ali Abdallah Saleh has met British ambassador Tim Torlot to discuss the attack, Reuters reported.
The other attack happened inside the compound of the Austrian gas company OMV in Haddah on the outskirts of Sanaa. The compound was surrounded by security forces and the gunman was eventually disarmed.
In a statement, OMV said the French national who died had worked for OMV as a procurement officer. It said that the UK contractor, who worked as an expert within the branch office, was being treated in hospital for serious injuries.
The company said it saw no political background for the action taken by the Yemeni security guard.
OMV is in contact with the contractor companies and embassies to provide full support, it said.
The attacks come two days after Yemeni authorities tightened security around embassies in the capital amid warnings about a planned strike by al-Qaeda.
"These twin attacks reinforce the overall picture that the security situation in Yemen has been deteriorating since the start of the year, since the Yemeni government and the US stepped up their fight against al-Qaeda," said Nicole Stracke of the Gulf Research Center in Dubai.
In April a suicide bomber threw himself at the British ambassador's two-car convoy in Sanaa as it neared the embassy compound.
The blast injured three passers-by and damaged a police car.
Al-Qaeda in the Arabian Peninsula (AQAP) later claimed responsibility for the attack.
The embassy was closed for two weeks as a result.
Yemen has been plagued by decades of poverty and instability, and its high numbers of unemployed youths are seen as potential recruits for Islamist militant groups.
More than 40% of Yemen's population live on less than $2 (£1.25) a day.