A rocket from Gaza struck the Ashkelon region of southern Israel on Thursday around 5:30 p.m. according to an Israeli military spokesman, causing no damage but putting into danger an already tenuous cessation of hostilities.

Israeli military sources also denied that a new ceasefire had been put in place but said that "calm will be answered with calm" according to an Israeli media report, echoing statements from top officials in Islamic Jihad earlier Thursday.

Israeli news website Ynet reported that an unnamed Israeli security source said that no new ceasefire agreement had been reached, but that Israeli forces would not launch any unprovoked attacks, in keeping with the terms of the 2012 ceasefire.

Despite this, earlier in the day Israeli armed forces called up its air force reserves, Israeli newspaper Haaretz reported.

The decision to call the reserves was made by Israeli defense minister Moshe Ya'alon in the cabinet. According to a military source, calling up reserves requires the approval of the Knesset security and foreign committee, and a waiting period of 48 hours, the report said.

Senior Islamic Jihad official Khalid al-Batsh earlier on Thursday had said that his movement would adhere to the calm "on condition that the occupation adheres."

The rocket comes after Egyptian intervention allowed the re-activation of a truce between Gaza militants and Israel, after Israeli air forces bombarded more than 30 targets across the Gaza Strip overnight and on Thursday morning.

The bombardment, which injured three Palestinians, came in response to the firing of dozens of rockets by Islamic Jihad on Wednesday, which themselves were a response by the group to Israel's killing of seven Palestinians -- including three of the groups' members -- in separate incidents earlier in the week.

A major eight-day confrontation in November 2012 between Israel and militants from Gaza claimed the lives of 177 Palestinians, mostly civilians, and six Israelis.

Smoke rises following an Israeli air strike in Rafah, in the southern Gaza Strip,
on March 13, 2014 (AFP/Said Khatib)

'Resistance is the right of the Palestinian people'

On Wednesday, spokesman for the Gaza Strip government Ihab al-Ghussein said that Israel is "responsible for any escalation," warning of the "consequences of any escalation" and reiterating that "resistance is the right of the Palestinian people to defend itself."

Israeli Defense Minister Moshe Yaalon, however, blamed both Islamic Jihad and Hamas, saying the latter was responsible for any fire emanating from its territory.

"Hamas is responsible for the Strip and if it does not know how to prevent fire on Israel from its territory, we will act against it and all of its broader interests," Yaalon said.

"Anyone involved in firing on Israel will be taking his life in his own hands."

Hamas is in control of the Gaza Strip government and maintains a fragile ceasefire with Israel, but other groups occasionally launch attacks.

Israel has repeatedly violated the ceasefire in the last year by launching attacks into the Strip and opening fire on civilians near the border, and militant groups often respond with rocket fire, which mostly falls in open areas.

Israel has also maintained a severe economic blockade on the Gaza Strip's 1.5 million residents since 2006.

The blockade has severely limited the imports and exports of the Gaza Strip and has led to frequent humanitarian crises and hardship for Gazans.