Gunmen on Monday kidnapped a European oil employee in Sanaa, hours after Yemen's capital was rocked by overnight explosions, in the second abduction of a Westerner in four days.
The renewed violence in the capital comes as the government struggles to end fighting between Shiite Huthis and powerful tribesmen in the north, and seeks to turn the Arab republic into a federation.
An oil sector official said the latest kidnap victim was a Briton who worked in the industry, although there was no immediate confirmation of this.
"Gunmen in a car kidnapped the British man at around 9:00 am (0600 GMT) near a grocery store in Hada," a heavily patrolled district in central Sanaa where several embassies are located, the official told AFP.
Witnesses said the kidnappers struck the victim on the head with the butt of a rifle, before driving him off.
The British embassy could not immediately confirm the reported abduction.
"We are aware of the news. We still cannot confirm," a spokesman told AFP.
On Friday, tribesmen abducted a German in Sanaa and later said they had snatched him to press authorities to release jailed relatives.
The foreign ministry said the German is being held in a tribal region in the eastern province of Marib.
Hundreds of people have been kidnapped in Yemen over the past 15 years, mostly by tribesmen who use them as bargaining chips in disputes with the government. Nearly all have been freed unharmed.
Al-Qaeda militants have also abducted foreigners in Yemen and is currently holding a South African man, as well as a Saudi and a Yemeni diplomat.
In another indication of the growing unrest, explosions that rocked the capital turned out to include two Katyusha rockets fired from a suburb, according to the country's supreme security committee.
Police had also said a mortar round exploded near the French embassy overnight, and a car bomb went off metres (yards) away in the Hada diplomatic district.
The mortar round hit shortly after a car bomb exploded on the nearby main road, near the residence of former president Ali Abdullah Saleh, the source said.
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Two other explosions near the defence ministry caused no casualties, police said.
But the security committee statement said some of the explosions thought earlier to have been the result of car bombs were rockets fired from the district of Sanhan, southeast of Sanaa, according to a statement carried by state news agency Saba.
The French foreign ministry said there was no indication its embassy had been targeted.
Yemen eyes ceasefire in north
Saleh continues to play an influential political role and is accused by critics of trying to destabilise the country since an uprising led to his ouster in February 2012.
Meanwhile, President Abdrabuh Mansur Hadi sent Sanaa governor Abdulqader Hilal to the northern province of Amran to try and broker a ceasefire and end bloody clashes there.
Scores of people have been killed in a month of combat between Huthi rebels and members of the powerful Hashid tribe that erupted on January 5.
On his Facebook page, Hilal said both sides had welcomed his mediation efforts and agreed to sign a deal on a "ceasefire, opening roads, and the withdrawal of fighters".
Tribal sources said fighting that raged last week, killing an estimated 150 people and wounding 400, subsided on Monday to allow mediation efforts.
The Huthi rebels have been advancing from their stronghold in the mountains of the far north to other areas nearer the capital to expand their hoped-for autonomous area in a promised federal Yemen, political sources say.
Hadi has pledged that Yemen will adopt a federal constitution in a bid to address local grievances that have fuelled violence across the Arab world's poorest country.
But at a ceremony last month to mark the conclusion of a troubled 10-month national dialogue, he postponed any decision on the thorny issue of how many components it will have, promising a special commission will decide.
The prospect of a federal Yemen was originally mooted as a way to address grievances of the formerly independent south, where secessionist violence has also been rising.
On Monday, gunmen ambushed the deputy head of police intelligence in Aden, Lieutenant Colonel Awad al-Dahbul, in the Khor Maksar neighbourhood, a security official said.
Dahbul and three of his guards were wounded, the official said.