The government of Ukraine ordered has prohibited all men from the ages of 18 to 60 from leaving the country so that they can be ready to defend against Russian forces. According to HITC:

Ukraine has temporarily banned men aged between 18 and 60 from leaving the country.

Ukrainian President Volodymyr Zelensky ordered a general military mobilisation after Russia’s invasion in the country in the early hours of Thursday.

The Ukrainian government imposed a ban which restricts men from leaving the country.

In a new declaration signed on Thursday, Zelensky has imposed a martial law and temporarily restricted all men aged 18-60 to leave the country “in order to ensure the defense of the state, maintaining combat and mobilization readiness of the Armed Forces of Ukraine and other military formations”.

A martial law means that military officials can impose laws on civilians for the duration of it.

“The State Border Guard Service of Ukraine reports that due to the imposition of martial law in Ukraine, a certain category of citizens is temporarily restricted from leaving Ukraine,” Ukraine’s interior ministry said in a statement.

“In particular, male citizens of Ukraine aged 18 to 60 are prohibited from leaving Ukraine. Such a rule will apply for the period of martial law. We ask citizens to take this information into account.”

Zelensky encouraged people who are willing to fight to come forward.

Meanwhile, tens of thousands of Ukrainians, mainly women and children, have been fleeing to Poland and other countries. As we read in Reuters:

SIGHETU MARMATIEI, Romania, Feb 25 (Reuters) – Tens of thousands of Ukrainians, mostly women and children, crossed into Poland, Romania, Hungary and Slovakia on Friday as Russian missiles pounded the capital Kyiv and men of fighting age were told to remain.

Many waited for hours in freezing conditions to leave Ukraine after Russian President Vladimir Putin launched the invasion, with lines of cars snaking for several kilometres towards some border crossings.

In Poland, which has the region’s largest Ukrainian community of about 1 million people, authorities said wait times to cross the border ranged from 6 to 12 hours in some places.

At Medyka in the south of Poland, some 85 km (50 miles) from Lviv in western Ukraine, roads were packed with cars, police directing traffic, and people hugging loved ones after they arrived on the Polish side. An internet map site showed a third of the way congested with heavy traffic at one point on Friday.

“It is only women and children (coming through) because for men it is forbidden. We leave all our fathers, men, husbands at home and it feels like shit,” said Ludmila, 30. When asked if she was worried about her husband, Ludmila broke down in tears.

Ukrainian rules restrict men aged 18-60, who could be conscripted, from crossing the borders.

Marta Buach, 30, from Lviv, said her husband was not allowed to cross with her at Medyka. “In Lviv it is ok but in other cities it is really a catastrophe. Kyiv was shelled, other small cities were shelled, we were hearing bombing everywhere,” she said.

…

Border authorities said 35,000 people had entered Poland from Ukraine since Thursday, while in Romania, roughly 19,000 Ukrainians had arrived in two days.

Poland’s deputy interior minister Paweł Szefernaker said Ukrainian bus drivers were unable to drive across the border as conscription-age men were being held back.

Michał Mielniczuk, a spokesman for the southern Polish region of Podkarpackie, said temporary accommodation was being offered to people arriving.