KIEV, June 17 -- At least 31 Ukrainian troops were wounded during clashes with rebels in eastern Ukraine near the border crossing with Russia early Tuesday, authorities said.

The fighting began near the village of Alekseevka at about 2 a.m. local time (0000 GMT), when insurgents attacked Ukrainian forces with mortar bombs, according to Ukraine's border guard service.

A total of 20 Ukrainian servicemen and 11 border guards were injured during the 40-minute fight and two seriously injured soldiers were taken to hospital for treatment, the border guard press service said.

However, it gave no figures on rebel casualties.

Since the start of the "active phase" of the government's military operation to retake towns seized by insurgents in eastern regions, at least 125 Ukrainian servicemen have been killed, according to official data.

On Monday, Ukrainian President Petro Poroshenko said he would unveil a detailed peace plan to end violence in eastern Ukraine in the near future and voiced hope of a ceasefire by the end of this week.