Britons warned to leave Yemen ahead of Friday protest (VIDEO)

Britain has warned its citizens in Yemen to leave the country as soon as they can, ahead of a planned day of marches in Sanaa on Friday, which is prompting fears of fresh violence after more than 50 deaths last week.

The Yemeni government declared a state of emergency Wednesday and up to ten thousand protesters gathered near Sanaa University on Thursday, calling for President Ali Abdullah Saleh to leave office immediately, Al Jazeera reported. 

Anti-government protesters have camped in Sanaa's university square in their thousands for the last six weeks, hardening their stance against Saleh.

Meanwhile, political analyst Abdul Ghani al-Iryani, speaking to Al Jazeera, warned of the risk of civil war has been heightened by clashes between the army and the presidential guard, which is commanded by Saleh's son, Ahmed.

Major General Ali Muhsin al-Ahmar, widely seen as the country's second-most powerful figure, said earlier this week that he was supporting pro-democracy protesters and joined calls for Saleh to leave office after three decades in power.

Ahmar was one of several top military figures to defect to the anti-Saleh movement several days after forces loyal to Saleh opened fire on protesters following Friday’s noon prayers, killing dozens of people, including children.

"With the military divided, the risk of confrontation and escalation is just too great. Right now it's at a very low level, and it won't start an all-out battle, but the risk is still there," Iryani said. 

Iryani said Saleh's offer to step down at the end of this year was "too little, too late."

British Foreign Secretary William Hague, meanwhile, told parliament Thursday that transport from Yemen could be affected if the security situation worsened, and some U.K. citizens who had not left the country despite an initial warning on March 12 could be stranded, Sky News reported.

Britain has already withdrawn its embassy team from Sanaa.

"Commercial flights to and from Yemen are still operating although could clearly change," Hague said. "Should there be further violence in Yemen, normal means of leaving particularly through the commercial airport in Sanaa could be blocked and the ability to travel around Yemen will be severely restricted.

"I want to make absolutely clear that all British nationals remaining in Yemen should leave without delay."

Meanwhile, police in Dubai said they had foiled an attempt to smuggle 16,000 handguns into Yemen from Turkey, said to be worth $4.36 million, Al Jazeera reported.

Dubai's police chief, Dahi Khalfan Tamim, said it was unclear who were the intended recipients of the weapons, comprising the biggest arms bust in the Emirates' history. But they were "definitely not [going] to the government," he said.