MOSCOW — Ukraine’s president signed off Wednesday on orders for limited martial law amid a showdown with Moscow over the seizure of Ukrainian naval vessels and crew, but the next moves by Kiev appeared caught up in internal political wrangling.
The crisis, triggered Sunday by a maritime clash in the Black Sea, has brought widespread denunciations of Russia and calls by some leaders in Europe for deeper sanctions on Moscow. But the political fortunes of Ukrainian President Petro Poroshenko have become part of the tensions. The deeply unpopular Poroshenko faces an election next year, and some critics — especially Russian President Vladimir Putin — question whether he is trying to use the standoff as a way to boost his standing.
The martial law process suggests how political concerns have spilled over into Ukraine’s response to Russia.
Lawmakers and government leaders haggled over the length of martial law — cutting down Poroshenko’s original 60-day proposal to 30 days to prevent possible interference in elections March 31.
Earlier Wednesday, Ukraine passed a resolution to schedule next year’s vote as previously planned, seeking to cement a promise Poroshenko had made to NATO Secretary General Jens Stoltenberg when appealing for assistance.
‘‘Poroshenko wants to get a head start in his election campaign,’’ said Maxim Eristavi, a nonresident fellow at the Atlantic Council. ‘‘He is playing the card of commander in chief, flying around in military uniform trying to project that he is the one in control.’’
Still, it was unclear when martial law would take force in 10 of Ukraine’s 27 regions, where the country has a sea or land border with Russia.
By law, the order must be published by the Ukrainian government’s newspaper, which could happen Thursday.
It would mark the first time Ukraine has imposed martial law in its conflict with Russia, which began in 2014 when Moscow annexed Crimea and supported pro-Moscow separatists in eastern Ukraine. More than 10,300 people have been killed in the fight against militias in the breakaway regions.
‘‘People wanted martial law four years ago, and Poroshenko was against it,’’ said John Herbst, who was US ambassador to Ukraine from 2003 to 2006.
In Moscow, Putin took direct aim at Poroshenko, claiming he is seeking political gain. ‘‘The incident in the Black Sea was a provocation organized by the authorities and maybe the president himself,’’ Putin said.
Russia seized three Ukrainian vessels in the Black Sea and captured 24 sailors, leading the international community to call for their immediate release. Russia said on Wednesday that all 24 had been ordered detained for two months.
‘‘[Poroshenko’s] rating is falling . . . so he needed to do something,’’ Putin said at a banking conference in Moscow.
On Wednesday, there were media reports of military movement on both sides.
A Russian navy ship was seen moving toward the Sea of Azov from the Black Sea, while Ukraine’s Odessa region said its air defense forces were put on alert. Moscow said it may deploy its S-400 air defense system to Crimea by the end of the year.
Ukraine has also asked NATO to reinforce the Black Sea with battleships.
‘‘We are waiting for our European and American partners. Ukraine sent a really strong signal that society is united,’’ said Oleksiy Ryabchyn, a Ukrainian lawmaker from the opposition Fatherland party. ‘‘Russia shelled our boats, they captured our people, and they try to blame this on politics. But martial law is about military aggression first. The politics will come later.’’
On Tuesday, Poroshenko said he hoped President Trump would deliver a pointed message to Putin when the two meet this weekend in Argentina at the Group of 20 summit. Trump has avoided direct comments on the tensions.
But the US special envoy for Ukraine, Kurt Volker, said Washington sees no reason to doubt information from Ukraine that its vessels were operating within international maritime rules when they were fired on and seized by Russian border guards, the Associated Press reported.
‘‘There’s no conceivable justification that we can think of for the use of force in this scenario,’’ Volker told reporters in Berlin.